Four different safeties were used sequentially on production versions of the C-96.
First type This safety was very much like that described and shown in the original patent. Here are illustrations from US patent 584,479 (issued June 18, 1897). 
On the real guns, the detent grooves g8 were a bit higher and further aft (ie, to the right in the drawing) than shown in the patent drawings. Here is the safety lever, in place on the lock assembly of a prototype gun - 
The safety on Cone Hammers and Large Ring Hammers was trivially different from the prototype in the photo above - the safety lever knob had an axial hole which didn't go all the way through. Internal operation was as shown in the patent - 
An obvious drawback of this design is that the safety lever doesn't move very much between positions. The lever moves only ten degrees, so that the safety knob moves a mere 0.18 inches. The Swiss military trials of 1899 noted that it was not easy to tell if the safety was or was not engaged. At that time the Swiss were undecided as to whether an auto pistol should have an automatic safety (such as a grip safety), a manual safety (such as a thumb safety), or both. Mauser never tried an automatic safety, but by the time of the 1902 American trails, some unsung genius at Mauser had managed to cram a much better safety mechanism into an even smaller space than that of the old safety. That brings us to - Second type The obvious operational difference is that this safety lever is pushed up to engage (make safe), and pulled down to disengage - the opposite of the earlier type. This is generally not a good sort of change to make, as the opportunities for user confusion are obvious. But the new mechanism had compensating virtues. As the report on the American 1902 tests puts it, "The arc through which the safety-lock thumb piece works has been greatly enlarged, showing at a glance whether the hammer is locked or not and making it much easier to operate the safety lock.The safety lever was much shorter than the earlier version, and moved through an arc of about 50 degrees. This moved the safety knob about 0.87 inches. When the lever is in either position, it's very obvious. 
Second type safety engaged Second type safety disengaged Although the second type safety had a shorter lever, so that its travel arc could be greater, from the outside of the gun it looked longer. Compare the first type safety lever on the late Large Ring Hammer at left to the second type safety lever on the early Small Ring Hammer at right - 
The second type safety lever stuck so far out the aft end of the gun that the lid of the shoulder stock/holster needed a deeper relief cut to clear it. Aside from the external length, a useful identification feature is the knob on the end of the lever. The knob on the first type had a hole which doesn't go all the way through. Daylight is visible through the knob on the second type safety lever. This can be spotted from either side and is visible in even crummy photos, so it is often easy to see if a gun has its correct safety lever. The lock frame changed a bit. The pivot hole for the stub shaft moved back, from a position directly above the pivot hole for the takedown latch, to a point directly above the hole for the hammer pivot pin (which was still part of the sear spring). The detent notches also moved. 
The stub shaft on which the safety lever pivots and the tab which locks the hammer were combined, becoming a stub shaft with a big chunk milled off, turning it into a cam. 
The milled slots in the hammer were changed. The safety lever cam normally rides in the milled slot a. When the hammer is cocked (and held that way by the sear), the safety lever can be pivoted into the "safe" position, pushing its cam against the slanted surface of the milled cutout at b. This pushes the hammer back slightly so that it is held in position by the safety, not by the sear.
The same thing happens when the hammer is down. When the safety is rotated, the cam pushes against the slanted surface at c, drawing the hammer back slightly from the firing pin. The change in hammer position is seen below - 
The safety lever also locked the barrel extension or slide when engaged. A small clearance cut was taken out of the bottom of the left side of the barrel extension. 
When in the safe position, the safety lever blocks the barrel extension at that cut. When the safety is engaged, both the hammer (whether cocked or down) and the barrel are locked. Because the bolt is locked to the barrel extension by the bolt lock, the bolt is locked as long as the barrel is. 
This arrangement means that the barrel and bolt are locked when the safety is engaged, whether the hammer is cocked or down. So, the gun can't be cycled with the safety on. This may have been a big deal - in 1916 Germany modified its P-08s so that they could be cycled when the safety was engaged. This was a simple modification on the Luger, but might not have been so simple on the C-96. In any event, Mauser never made such a modification. Third type - the "New Safety" And now for the Big Problem with the second type safety. If the safety lever is not pulled down quite all the way to the "engaged" position, like so . . . 
safety "off" safety not quite "off" . . . and the trigger is pulled and then released, it is possible for the hammer to drop very slightly, but not all the way - just enough to drop past the sear. The sear is then held out of engagement by the hammer. The hammer is still cocked, and held there by the safety lever, but the sear can't catch it when the safety is switched "off". Then when the safety is switched "off", the hammer will immediately drop, firing the gun, even without a further pull of the trigger. Here is the complete lock assembly in the frame, without the barrel, bolt, bolt lock, etc. We are interested in the interaction of the sear a, the hammer b, and the safety d. Part of the lock frame is visible at c. 
Closeup, hammer cocked, safety "off". The hammer is resting on the sear - 
Closeup, hammer cocked, safety "on". The hammer is pulled back - very slightly - from the sear, and is held in the cocked position by the safety, not by the sear - 
Closeup, as above, but trigger pulled. Sear has moved upward very slightly. It doesn't look like much, but that's as far up as the sear goes when the trigger is pulled. Since the safety is fully "on", the hammer doesn't drop at all, and the sear will drop back into position when the trigger is released - 
The problem only occurs when the safety is almost switched "off". When the trigger is pulled, the hammer can fall just enough to prevent the sear from dropping back down - it doesn't take much, a few thousandths of an inch is sufficient. Then when the safety is switched fully "off" the sear is unable to catch the hammer, and the hammer drops. The solution Mauser adopted was to arrange for the safety to hold the cocked hammer considerably further away from the sear. In fact, it's held so far away that the hammer has to be manually pulled back slightly in order to engage the safety. In other words, the system no longer uses the safety lever itself to cam the hammer slightly back. Mauser couldn't just increase camming action to pull the hammer further away from the sear, because the whole problem is that the user doesn't pull the safety lever all the way back because he mistakes the force needed to make the safety lever cam the hammer back for the safety lever being all the way back, and therefore fully engaged - when it isn't. So, Mauser's solution was to force the user to perform that function manually, and very deliberately. And should he get lazy or forget, the gun will remind him when he tries to engage the safety, because it just won't go. Mauser called this modified safety the Neue Sicherung, or New Safety. Here is the New Safety in operation. With hammer cocked and safety full "on", compare a second type safety (left, on a Prewar Commercial) to a New Safety (right, on a Postwar Bolo) - 
serial # 104441 serial # 522022 Clearly, the newer arrangement holds the cocked hammer further off the sear. Therefore, when the hammer drops slightly when the safety lever is nearly switched "off", the hammer won't get under the sear even if the trigger is pulled. Voilà, problem solved .... at the price of operational convenience. It takes two hands to engage the New Safety if the hammer is cocked. I won't say it's impossible to do with one hand, but at best it's annoying. On the other hand, it reduces the possibility of the safety being engaged accidentally. The mechanical difference between the New Safety and its predecessor is all in the hammer. The mechanical difference between the New Safety and its predecessor is all in the hammer.
A new feature, perhaps accidental, is that when the New Safety is switched to "off", the hammer drops onto the sear with a distinct click, a good warning that the safety is indeed off, the hammer is cocked, and the gun is ready to fire. 
Except for the hole through the knob, the safety levers of the New Safety and the earlier (Second type) safety are identical, and when interchanged retain full functionality. The hole itself (or the lack thereof) has no functional purpose - it is only a recognition feature. New Safety guns always had solid safety lever knobs, and guns with the Second type safety always had knobs with through holes. They are often found mixed-up these days, with solid lever knobs on Second type safety guns and knobs with through holes on New Safety guns, and they'll work that way, but it's not how they left the factory.
Between the engraved intertwined N and S monogram on the back of the hammer and the solid safety lever knob, the New Safety is easily distinguished in aft or side views. → The New Safety, while superficially clumsy, is ingenious. Operationally, the only tedious part is engaging the safety. The process of disengaging it isn't inhibited at all, so a cocked gun with the New Safety engaged can still be fired quickly. And any Prewar Commercial could be updated to New Safety configuration by simply replacing the hammer and the safety lever. Guns in the Prewar Commercial serial number range are occasionally seen with the New Safety, even though that appeared long after the guns were manufacured. So obviously they're been updated to New Safety specs. Actually reworking the original hammer to New Safety specification would have involved moving a milled slot - not absolutely impossible, but very expensive. The old slot would have to be filled by welding, the part heat-treated for stress relief, and the new slot milled. Ouch. So gun updates, at least as performed at Mauserwerke, undoubtedly involved new hammers. To finish the jobs the new hammers would have to be numbered to their guns - all guns of this period had numbered hammers. Observed specimens indicate that factory reworks of older guns to New Safety specification had their old hammers and safety levers replaced with the new types - the factory didn't just replace the hammer. So, once again - any New Safety gun, either original factory production or later factory rework, had a safety lever with a solid knob. No other C-96 variant had a solid safety lever knob. Any odd combination seen today is a later swap of the safety lever. The two types of safety lever are functionally and dimensionally identical. And, since safety levers were usually not numbered to their guns, the only way to tell the two apart is by the presence or otherwise of a through-hole in the knob. Now to hit the books for a little history. As usual, things are a bit muddled. Belford & Dunlap (The Mauser Self-Loading Pistol, page 108) claim that the New Safety was introduced at serial number 200,000, quoting a translation of a letter from Herr August Weiss as authority - ". . . from serial number 200,000 Mausers were made with the new style hammer with an improved safety. The push button of the 'Sicherung nue art' (Safety-device new style) is not bored through but is solid. If the safety, before the change, was not pushed to the deepest position, the weapon could automatically go off safe. This change was indicated on the hammer with 'SN' . . ."Erickson & Pate (The Broomhandle Pistol, page 90) have this to say about it - "At the beginning of the war officers were offered Model 1896s in 7.63 Mauser caliber with or without stocks through government armories at 60 Marks (U.S. $15). By early 1915 such purchases could be made direct from the factory. These early sales were of standard pre-war commercial pistols, and problems with the safety soon became apparent: with slight wear, the safety would allow premature discharge. Mauser moved quickly to correct this fault. In September 1915 it was requested that faulty pistols be returned for repair at the factory. In November 1915, at serial number 280,000, the improved safety, with an undrilled safety lever and a modified hammer marked NS (Neue Sicherung, New Safety) on the back, went into production. This was the beginning of the wartime commercial model. Some pistols with the new safety will be encountered before the 280,000 serial range, but these are thought to be the factory reworks."More general works such as Pistols of the World (Hogg & Weeks, Revised Ed., page 164) give 1912 for the date (conflating the event somewhat with the change from four to six groove rifling, which had in fact happened some years before the advent of the New Safety), going so far as to call the modified gun the "C/12". Myatt's books seem to follow Hogg & Weeks. Unfortunately no documentary authority is offered for any of this, though the evidence I've found basically supports Erickson & Pate. Fortunately we do have some contemporary documentation. Forum member Stucki has called attention to a page appended to an undated owner's manual for what we nowadays recognize as the Prewar Commercial. The page itself is dated October 1915, and it gives instructions for the operation of the New Safety. 
My translation -
I consider this decent confirmation that
1. the solid safety knob was unique to guns with the New Safety, as I stated above,The New Safety, with its monogrammed hammer and solid knob, is the only feature which distinguishes Prewar Commercial guns from their Wartime Commercial successors. So these modern names aren't strictly accurate. Since the war started in August of 1914, guns made between then and late 1915 were literally "wartime" guns, but we still call them Prewar Commercials. The New Safety equipped all Wartime Commercials, 1916 Prussian Contracts, all the immediate postwar oddballs, all Postwar Bolos, and the small batch of proto-M-30s made shortly before the M-30 was introduced. The earliest gun I've seen with the New Safety is number 232232. This is probably one of the Prewar Commercials returned to Mauser to be reworked with the New Safety, and thereby brought up to Wartime Commercial specification. → It's basically impossible to tell just by looking at the gun if it had been reworked unless the typeface of the numbers is different. Very slight differences in the stamps of the numbers on the frame, lock frame, and hammer - the sort of differences which make you wonder where you left your magnifying glass - don't indicate rework. They're normal. Fourth type - the "Universal Safety" The Universal Safety was introduced with the M-30. Mauser did two things with this variant - • Gave the gun a hammer-drop safety. The safety didn't itself drop the hammer when engaged, but it prevented it from hitting the firing pin, so the hammer could be dropped the usual way - with the trigger - without firing the gun. This change required modifications to the hammer and the safety lever. • Locked the sear when the safety lever was anywhere between "engaged" and "off", eliminating the New Safety requirement to pull the hammer back to engage the safety. The hammer, safety lever, sear, lock frame, and barrel extension required modifications. The hammer-drop function was easily accomplished by a change in the hammer milling. Here are the hammers for the New Safety and the Universal Safety - 
The two notches at a and b which locked the New Safety hammer in its cocked or dropped positions don't appear on the Universal Safety hammer. Even when engaged, the Universal Safety doesn't lock the hammer in either position. Instead, when the safety lever cam is in the "safe" position, it prevents the hammer from hitting the firing pin by blocking it at c. This avoids the problem which the New Safety was devised to solve. Since the safety never holds the hammer in the cocked position, it can't inadvertently let it drop below the sear. The cocked hammer is kept cocked by the sear, whether the safety is engaged or not. A disadvantage is that if the gun is dropped on a cocked hammer, the inertial load will be taken by the sear, rather than the safety. Well, no system is perfect. When engaged, the Universal Safety holds the hammer back a bit further than the second type safety and New Safety. 
M-30 with Universal Safety External identification features are the hammer through-hole without the concentric rings (which has nothing to do with the safety per se, but this hammer style only appeared with the Universal Safety), the hole through the safety lever knob, the more extravagant shape of the safety lever, the slightly lower position of the knob, and, for the first time on a C-96, the F and S letters indicating safety position ("fire" or "safe"). 
Universal Safety (top) vs. New Safety levers New Safety (left) vs. Universal Safety levers The arrows show where the hammer contacts the New Safety and Universal Safety levers when on "safe". The rectangular tab at about 7 o'clock on the end of the New Safety stub shaft is what keeps it from falling off when the gun is field-stripped. On the Universal Safety lever, that tab has been enlarged, and moved a bit to serve double duty - keeping the safety lever in place when the gun is stripped, and holding the hammer back even further from the firing pin when the safety is on "safe" and the hammer is down. In that condition, the hammer is lowered onto the bolt (and the firing pin) with a nice gradual motion when the safety is switched "off" - gradually enough that the firing pin doesn't move when the hammer comes to rest against it. Compared to the New Safety lever, there's more steel in the cam area of the Universal Safety lever, so wear will affect it less, and it has about twice the shear strength, to resist fracture when it's whacked with the hammer. Because the retaining tab moved, the lock frame had to change. Here at top is the lock frame of a New Safety gun, and below it the lock frame of a Universal Safety gun. The circled areas show that the clearance cut for the tab was enlarged a bit, and moved from 6 o'clock to 3. 
The more complex shape of the safety lever allows the letters F and S to show when appropriate. The portion carrying the F is higher than it was on the Second type or New Safety. To compensate, the cut in the barrel extension was enlarged. 
Postwar Bolo with New Safety vs. M-30 with Universal Safety The big change, the angled slot for the safety lever to lock into, is at a. The new cut is large enough that the lightening cut at c was moved forward a bit. The cut at b was moved forward by the same amount, although there was no functional reason to do so. The bevel at e was deleted, again because the safety cut at a is so large. The bevel at d was deleted, apparently just to keep things symmetrical. Now for the new mechanism, which locks the sear when the safety lever is in an indeterminate state between F and S. An extension was added to the Universal Safety sear - (identical to earlier sears) 
Universal Safety sear The lock frame was modified to allow the sear extension to cross over to the left side of the gun. Here are the partial lock assemblies of, at top, a Postwar Bolo with the New Safety, and, below, an M-30 with the Universal Safety, both with their sears in place but their safety levers removed. 
The same, with the sears removed. Note the additional cut in the M-30 lock frame at a. 
The safety lever of the Universal Safety engages the sear extension, preventing the sear from moving unless the safety is in the F or S positions. Here is the safety lever at F, at an indeterminate midway position, and finally at S - 
That little tip on the sear extension sticks up above the edge of the frame, and even further when the trigger is pulled and the sear is raised ..... 
.... which would cause an interference with the barrel extension on recoil. 
But since the barrel and barrel extension don't recoil very far, Mauser was able to provide enough room to clear the sear extension by removing a small amount of material inside the angled locking slot for the safety lever. It's that shallow drilled hole, buried in the slot -
The other conspicuous change to the lever of the Universal Safety is that an inspection mark was added to the inner (right hand) face. Earlier safety levers don't have any such mark. Here are two specimens from serial numbers 881837 and 918367 - 
Lacking documentation, we can only speculate as to just what was being inspected when these stamps were put on. Perhaps Mauser had set up a non-destructive strength test for this specific part. It would have been only sensible, considering the load the hammer could put on it.
I never use the hammer drop safety, on the M-30 or any other gun. I use the thumb technique, which has the general advantage of working on most any gun with an external hammer, no matter what sort of safety it has. The thumb technique isn't for everybody, as one needs fingers of a certain size, and sufficient dexterity to lower the hammer relatively gently. 
Fortunately, it's not as painful as it looks. Experimental safeties Strictly speaking, more than the four safeties I describe above might be encountered on the C-96. But they seem to have been experimental, and only three or four specimens are known of each. System Mauser, pages 182-3; the Mauser Self-Loading Pistol, pages 73-6; The Broomhandle Pistol, page 126; and Know Your Broomhandle Pistols, page 69, all discuss the Gelenkscherung or Joint Safety, on a gun called, in Book and Collector land, the "1902 model" (as usual, that's not a designation used by the Mauser factory or sales organization). This was a perhaps overly complex mechanism which would cock the hammer when pulled back to the "fire" position, but when pushed forward again to "safe" would leave the hammer cocked but block it from striking the firing pin. Note that when in the "safe" position, the safety lever is forward and up - the same as the second type safety, the New Safety, and the Universal Safety. When this Joint Safety appeared, production C-96s had the first type safety - a short travel arc, on "safe" when the safety lever was pulled down. So the Joint Safety was an early attempt by Mauser to make a safety which worked somewhat like the later production safeties. But aside from that, what was the point? Quoting System Mauser, "The safety serves a two-fold purpose. In addition to its normal function [as a manual safety], it also permits one-hand cocking of the hammer - a feature almost impossible to duplicate with the conventional hammer types."
In any event, Mauser never put the Joint Safety into real production. System Mauser, on page 184, and The Broomhandle Pistol, page 131, identify another safety. This one switched the safety off automatically when the hammer was cocked. Guns with this feature have a peculiar variant of the small ring hammer. Again, only a few specimens are known, none of which have been examined by me. Failure Modes I have never broken a C-96 safety, nor encountered one with a broken safety. Common advice is to avoid using the hammer-drop feature of the Universal Safety, but I can't see any good reason to do so. Even if it should break, you're pointing the gun in a safe direction when you drop the hammer (aren't you?). Although catastrophic failure seems rare, there is a failure mode potentially shared by all four types of safety. The safety lever is held in position by a pair of detents cut into the lock frame. The nether end of the lever is formed into a leaf spring, with a triangular bit on the end which catches in the detents. Sometimes the leaf spring fails to do its job - for one reason or another it has lost much of its "springiness" and does an inadequate job at holding the safety lever in position. When the gun is fired, under recoil the safety can move to the "on" position - and then the next shot doesn't happen until the lever is manually moved back to where it should be. Not a dangerous situation, but certainly an annoying one. |
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Note that on the "odd" safety lever, the front edge of the lever is rounded, the "F" is considerably further aft, and the curve of the lever makes an akward detour over the "F". →
photo above. The gun in the photo is an oddball, with some other questionable features, so the late M-30 features - the unmilled barrel extension rail and late-style MAUSER banner - don't really imply that the "odd" safety might normally be found on late M-30s. I don't have enough data yet to make any reasonable hypothesis as to where and when - or why - the "odd" safety lever was used. And I've not yet had the opportunity to examine one up close, so I don't know if there are any internal or functional differences.
