The sidearm in this photo is probably a Model 10, possibly a Victory model. The first guns used by the Combat Defense Squadron, later the SAC Elite Guard, were chrome plated and had plastic stag grips. Most pictures from the early 60's show lanyard loops on the butt of the the chromed revolvers. By the time I arrived at SAC (1980), the Elite Guard was using the blue Model 15, just like every other Security Police unit in the AF.
I have a set of Ajax Staglite grips for my Model 15-4 that are a very close match to those in the photo.