S&W may have made some recent changes, but prior to that I'm pretty sure that the original design included the rebounding hammer safety.
The S&W hammer rebounds also. As I stated earlier, these guns were made under license, any changes made were approved beforehand. I'm still waiting to hear the whole story, and suspect that we will not hear it for a long time as lawyers and insurance people are involved.
When I say the whole story I mean that the actual problem has never been specified in detail. My own suspicion is that it is a metallurgical problem that has occurred in a small percentage of existing guns, a percentage of guns large enough to arouse the interest of the people mentioned earlier.
Walther engineers worked with S&W engineers in making the changes between S&W made guns and earlier Interarms, French Manurhin and even earlier German made guns.
Changes noted in an article in American Handgunner from 2003 (
http://findarticles.com/p/articles/mi_m0BTT/is_165_27/ai_105698452/) are as follows;
The tang was extended as noted.
The grip material was changed to Zytel.
The lower rear of the slide was aggressively deburred to minimize slide bite. (Which I carried even farther on mine.)
The trigger serrations were eliminated, reportedly they caused discomfort.
The barrel and frame feed ramps are cut after assembly instead of prior to, a clear improvement from an engineering standpoint.
Closer tolerances due to the use of CNC equipment.
The serial number engraving method.
No mention was made of any changes to the safety.
I took the safety out of mine and it is made of stainless steel. In my opinion alloy carbon steel is stronger and more durable than any stainless alloy but there may be disagreement on that by metallurgists.
We don't know whether or not they are swapping parts with a different alloy, perhaps 17-4 PH for 416 or visa versa, cast for machined, or changes in the safeties sectional area within weak areas. (I don't recall whether or not the safety appeared to be machined or cast) They may even just be inspecting them for casting voids or machining mistakes that have been discovered in failed guns, stamping the mark and sending them back.
If anyone knows anything more and can report it I'm sure many of us would love to hear the details.