I'm no expert, but I have extensive experience with the 4516's, so I'll try to help.
The no dash 4516 had a stepped frame, dual recoil springs, thinner slide with a rib along the top and flash chromed hammer and trigger. It is the lightest in weight of the 4516's. The Smith & Wesson rollmarks were twards the muzzle with the "four line" aft of it on the slide.
There reportedly were slide inertia problems resulting in feeding problems and also magazine issues. The original follower IIRC was problematic.
Many 4516 no dash owners report no issues at all with their guns and I believe them. But, there evidently were some problems with SOME 4516 no dash guns as S&W did some design changes.
The 4516-1 eliminated the step in the frame and beefed up the slide too. The step along the top of the slide was eliminated as well. Spurless hammer and trigger still flash chromed. Early versions had the rollmarks similar to the no dash but later production centered them on the slide and eliminated the "four line". The recoil spring was changed to a single unit. Magazines were modified with new followers and IIRC springs as well. The magazines were etched with an advisory "For use only in 4516-1".
Reportedly, there were still feed issues with SOME 4516-1's. Mostly well used examples in LE service were where problems were reported. Whether this was a design problem or user problem is up for debate, IMO. In any case, 4516-1 production dwindled and then stopped. I can't recall the year..........1992???
I think it is only fair to point out here, that while MANY 4516-1 owners have pistols which function perfectly, right out of the box, there are quite a few who report various feed problems. Not dozens or of epidemic proportions, but enough reports to warrant some concern. Some of those sent their 4516-1's back to S&W for examination and repair. They report that S&W modified their 4516-1's in the following manner. The guide rod was changed to the later, reduced diameter, 4516-2 version. A washer style retainer was installed in the guide rod tunnel of the slide and the dual recoil spring setup, ala 4516-2, was also installed. These owners report that upon return from S&W, their 4516-1's feeding issues were eliminated.
After a brief hiatus and a redesign of the recoil system the 4516 model was, according to the S&W flyer/announcement; "Back by popular demand" in the 4516-2 variant. The changes included the previously mentioned new guide rod and dual recoil springs, a redesigned frame with longer tang and blue/black forged hammer and trigger (Some very late production 4516-2 have black MIM hammer and trigger). I don't recall positively as I sometimes have oldtimers,
but I think the larger barrel hood and other 3rd gen 45 barrel modifications were also incorporated into the 4516-2. Perhaps someone here can confirm or correct that. This was around 1994/1995 IIRC. Also at around this time the last revision of the magazines occured with the incorporation of the black followers.
Incorporating all of the design enhancements and none of the later cost cutting measures (except for those examples having MIM hammers and triggers) the 4516-2 were, and evidently remain, the most popular of the 4516 series.
After the end of the 4516-2 line......1999????? there was one more variant. Some LE really liked the 4516 for their plain clothes and detective divisions. S&W would make runs of certain models for LE. Thus the 4516-3. Visually, the 4516-3 is only discernable from a 4516-2 by virtue of its markings. The rollmarks are gone and replaced by laser etching. The slide has "Smith & Wesson" with the famous logo laser etched on the slide. The frame is laser etched "MOD 4516" above the trigger guard along with a laser etched serial number. There is no "dash number" after the "MOD 4516" marking. This creates some confusion as folks mistake these last 4516's for no dash models. The 4516-3 does incorporate the MIM hammer and trigger, dual recoil spring setup, MIM mag catch (replace this with a steel part if you use this gun for serious purpose as mine failed) and larger barrel hood. The 4516-3 is known at S&W as a 4516 R4, or revision 4.
If you have the original box, up on the right side you will see and "03" and "SPECIAL ORDER" on the label. This almost always confirms an LE overun after the end of "official" production. Of course the only way to know for sure is a call to customer service or a Jinks letter.
For all intents and purposes, the 4516-3 is a laser etched 4516-2. So there you have it. A thumbnail 4516 history as near as I've been able to discover over the last twenty years.
Personally, I became enamored by the 4516 with a no dash model. It was a confiscated piece that was present on a "range day". Range day was a once or twice a year thing at my old agency where we used confiscted guns to "destroy" confiscated ammunition. And yes, we got paid to do it.
I picked the 4516 no dash out of a milk crate full of guns. I still recall one of the guns above it was a very beat up, peeling nickel Python with hideous lime green plastic grips. Anyways, it only had the one mag in it. I was searching for a compact 45 at the time as the writing was on the wall that our revolvers were going away for good. They would no longer authorize them so we better find a semi auto to use.
I fired around 500 rounds through that filthy, neglected 4516 no dash that day, IIRC. There was no lube at all on it when I started. After 200 or 300 rounds I remember the slide was getting slow. So I hosed it down with Breakfree and went on to shoot it the rest of the afternoon.
This gun was far more accurate than any of the "popular compact 45's" of the time. None of them were as reliable. All of them choked. Not the 4516 though. I wondered why I'd never heard about the 4516. I promptly called around and found a NIB 4516-3 which I proceeded to use for the next several years. A reliable accurate little tack driver. One of my never sell guns. I only retired it when I aquired the 4513TSW's. I still shoot it from time to time though. Sweet 45.
Hope this helps! Regards 18DAI