I have no details other than personal experience. I had a Model 10 issued to me (all of them 10-5's) in four different AV units. All our 10's were, taper 4", Round Butt, commercial blue, no military markings, nothing special about them (no lanyard loop, etc) at all. 100% commercial off-the-shelf. They were all fairly well worn in the finish department, as you can imagine. I never saw any square butt Model 10's, they were all RB. This was from 1985 to 1990.

We also had 4" Ruger Service-six with lanyard loop. They were round butt as well. Yeah, I know that should be a Speed-Six, but the frames were indeed marked "Service-Six". There was a "US" marking on the frame as well. Nothing else military specific, just "US" stamped on there.

I always had a choice, and I went with the S&W. It was lighter, and the trigger was better. While I am a big fan of the "-six" Ruger myself, I'm a bigger fan of the K-frame.

I was in the 1st Cav at FT Hood (493rd/F-227, E-227, HHC CAB) and B-3/501st ROK and it was the same in all those units. Choice of Ruger or Smith & Wesson. We had more than enough in any of the arms rooms to pick either model. After that I was at Campbell, and we had brand new M9's.

I know some of the dog handlers had revolvers as well. The idea being they could operate it with one hand easier, as they controlled the dog with the other. Female MPs were rumored to have them as well, but all the female MP's and some of the dog handlers I saw either had M1911A1s or later M9's. What the Army says how it's supposed to be , and how it really ends up being was often two different things.

We didn't shoot them much. I wasn't too impressed with the USGI .38 Special ammo. It was basically the same as WWB FMJ. All of my S&W's would have done the job though. They shot decent, and they were all actually in pretty good mechanical shape because we just carried them around. Massive finish wear, but they probably lasted forever.

I know the military had over 100,000 .38 revolvers of all makes, shapes and sizes before it finally bought the M9. They were bought in different batches as needed, by each service separately. So the variations are likely endless.

We had "Dirty Harry" shoulder holsters that didn't have any retention other than the steel spring and it was pretty obvious that in any kind of aircraft crash you'd loose the weapon. Most people wrapped the lanyard around it to retain the revolver because you certainly didn't want to loose one out in the field. Since the Model 10 didn't have lanyard loop, you had to do something with the stupid leash anyway. The Survival vest had a holster sewn onto it. I've seen leather ones, but all ours were nylon. We also had leather hip holsters that were typical GI design with the wire belt hanger. None of them were all that great. All were worn out ten times over. I used the shoulder holster usually because it was easier to sit at a desk or vehicle and simple enough to just swap over to the survival vest if I was flying. I used the hip holster only for parades, etc. where we had to use them.

I don't have any other info that I could say was factual. You have to figure that the way they bought and issued those things, there was no real "that's the one way it was" with .38's in the military.