Revolver is a Combat Masterpiece, later known as Model 15.
The USAF issued these, but not with target stocks. I will assume he bought one retail because he liked it, not that he stole his sidearm.

The serial number should be on the very bottom of the butt, but you would have to take off the target grips to see it.

The holster is a typical $6 hardware store job, not GI.