I've been carrying S&W 3rd gen pistols for about 15 years, and I've been a factory certified L/E armorer for about 5 years. I've been impressed enough with them to buy several of my own in recent years, and I've received outstanding service from them. The later production 3rd gen pistols have benefitted from noticeable improvements in production methods.
There's really no way to actually know, however, how well maintained a pistol was while used by any L/E agency ... let alone whether or not it was fiddled with by the individual user to whom it was issued. Sometimes cops can get "creative" when it comes to "just knowing" they can fix something and make it even better.
Also, as pistols reach a point in their service life where they've been subjected to a lot of use and/or abuse ... or simply were in-service for 10+ years, even if only actually shot 1-4 times per year ... it's a good idea for them to be carefully inspected for general wear and worn parts, springs, etc.
Extractors & extractor springs can become worn with age & use. As extractors age sometimes the edges can become "work-hardened" and brittle, and perhaps chipped/broken ... and maybe damaged, if the previous user made a practice of loading the chamber "directly", instead of from the magazine
... and extractor springs may become weakened to the point where they allow extractors to slip over case rims during recoil. These are easy things for a gunsmith familiar with S&W pistols, factory trained armorer or a factory terchnician to diagnose and correct, though.
The early 3rd gen ejectors were short and had a sharp angle on the bottom, while the later production ejectors were longer (for faster, earlier ejection) and were rounded on the bottom (mitigating any potential stress risers).
Sear release levers may become worn out of spec when it comes to decocking timing.
Drawbars should be checked for stress risers and cracks. The newer production drawbars in recent years are much better machined (forged & extruded) and have been "rounded" in areas where some cracks used to occur (albeit not that often).
Also, in recent years S&W has taken to recommending that recoil & magazine springs be replaced every 5,000 rounds or 5 years. That doesn't mean that everyone does it, though ...
If in doubt, I'd simply ask the gunstore if their gunsmith did detailed inspections of the pistols when they received them, or whether they were previously inspected by the factory after being turned in by some agency.
S&W pistols can provide outstanding service to owners ... despite the political diatribes often waged against them.
I don't own S&W pistols exclusively, either, so it's not like I work for them or anything. For each and every problem experienced with a S&W pistol, I can relate a problem experienced with just about EVERY other make, model & caliber of pistol in common L/E use, too. You name it ... Colt, SIGARMS, Beretta, HK, Glock ... and I can either recall an instance where either something broke on our range, or else I know another L/E armorer who had things break. That's why we have armorers and factory reps, you see ...
