The 2nd and 3rd generation nomenclature was to market significant redesigns of the 1950s model 39 platform. Regardless of when they were introduced or how they were named, all pistols that are not direct descendants of the 39, 59 or 52 are not younger generations of those pistols. That rules out all 1911s, polymer framed pistols and .22s.

The most important design changes separating 3rd gens from 2nd were not machining the back strap as part of the frame to reduce trigger reach giving more leverage DA and press fitting barrel bushings to improve accuracy. As with all S&W engineering changes transitional pistols were assembled to use up parts inventory and I vaguely recall some 3rd gen features appeared first in 669 size pistols, but in general a wrap around one piece grip and non-removable barrel bushing = 3rd generation.

While I’m not a 3rd gen expert I’m well established as a forum curmudgeon, so until I’m contradicted by a certified master curmudgeon, that’s my opinion and I’m sticking to it.