Originally Posted by carguychris:
In terms of standard-production M5906 non-TSW production changes, there are 3 important ones.
In 1990, S&W switched from a vertical blade-style rear sight on the fixed sight pistols to a steeply slanted Novak Lo-Mount sight. The optional screw-adjustable rear sight was not changed. (Make note that the three types of sight do NOT interchange due to different-sized dovetails in the slide!)
Around 1992-1993, S&W changed from the square trigger guard to a round trigger guard. Round guard pistols will generally fit in square guard holsters but NOT the reverse. FWIW S&W later made a couple of minor changes to the shape and checkering on the round guard, but these changes are subtle and probably inconsequential unless you're a collector.
Between 1993-1996, S&W started using MIM hammers and triggers on many 3rd-gen pistols, and by 1997 they seem to have switched to MIM more or less exclusively. (According to collector research- i.e. "this is what my gun has on it, how about yours"- there does not seem to be a hard-and-fast cutoff date.) Unlike the constant wailing and gnashing of teeth about MIM on S&W revolvers, most 3rd-gen fans seem to agree that the MIM parts were a Good Thing, because they give the MIM guns smoother, more consistent, and seemingly lighter triggers. The MIM parts can be ID'd by mottled dark grey finish, skeletonized or cutout sides on the MIM hammers, and a slightly different shape to the step at the top of the MIM triggers. (Be aware that dark finish is NOT a surefire indication of MIM on stainless guns, because S&W also used 5904-type blued parts on the stainless guns from time to time!)
Wow, thanks for this. I was unaware that the timeframe for the rounded guards and MIM change-over was so tight.
The two 5906s I have (round trigger guards, non-MIM hammers/triggers) were purchased during the late 1992 - early 1993 timeframe within a few months of one another. One was a duty weapon, the other remains NIB to this day waiting for my son to inherit it when he comes of age.