Recently purchased a 5906 and noticed that my grip is like the one in the picture on the right...not upgraded. I called S&W and they no longer honor the recall due to no parts. After talking to customer service and sending this picture in, she checked with someone named Mark who has worked there for 45 years and has worked on these guns a lot. He said that the picture on the right is actually the upgraded one as it has the small dimple on the very back of the grip and that the one that is "upgraded" is a mold mark made by a different supplier. I'd like to make sure I have a reliable grip, but not sure who's right. Any thoughts?
There are still some people working at the company who were probably around for the original AIP period (Auto Improvement Program, which resulted in the 3rd gen models), and I'd not quickly discount someone still working being able to remember this grip material change and being able to give you the right info.
(Of course, there are fewer of them still there, and those remaining numbers are getting closer to retirement all the time. One of my longtime LE parts & armorer contacts, who was involved with the original 645/4506 guns, retired a little while ago.)
Anyway, I have some used double stack 9/.40 grips in my spare parts, both full-size & compact, as well as a couple of grips from the original TSW 9/.45 guns and even a couple of both (still) new & used full-size .45 grips.
The .45 grips & new production 9 single stack compact grips exhibit the "softer" molded dimple next to the mag well, but the older double stack 9/.40 grips are a mix of having dimple or punch marks on each side of the U-notch cut window, meaning next to the mag well or at the rear of the grip. The smaller punch marks are located somewhere (variably, or even sloppily) toward the rear of the grip, and are smaller and "sharper" in appearance.
It's goes back a ways, but our original 3rd gen duty guns were from the early '89/'90 production, and we later got a huge box of replacement grips when they changed the grip material (the "recall"), and I remember seeing them with the smaller punch marks to the rear of the grip. I also remember being told they were being hand-marked back then, which would explain the somewhat "inconsistent" placement of the punch marks on different grips.
We were told in an armorer class that as long as the new grips exhibited a dimple or punch mark on either the front (near mag well) or rear (behind U-notch cut) of the bottom of the grip, it was the revised ("upgraded"), stronger grip material.
Also, FWIW, I remember being told that the company's decision to change the grip material had resulted from a very, very small number (a few?) grips that had suffered cracking when being dropped onto a hard surface. S&W still commanded a strong segment of the LE market back then, so there were a lot of guns in-service.
I'd not be surprised if they were getting their grips made by more than one vendor back then, either, because we were sometimes told that the same thing happened with other plastic parts from time to time. (I also remember being told that they usually used a couple of different vendors for both mag bodies springs.)
I've told my stories before (successes, failures and outright BS thrown at me) so I won't repeat them again... but PLEASE S&W!!! Make up your minds!!! Are you still honoring the recall or not? 
