From my undertanding, small caliber pistols were issued by the various branches of the service to staff officers (Colonel would qualify), generally .32ACPs or .380ACPs, generally as a set with holster and spare magazine. I suppose a .25ACP might have been issued. It is also possible that it was privately purchased and carried as a pocket gun (FWIW, it was a "gentlemanly" thing to do). Hard to say without documentation!
Never try to educate someone who resists knowledge at all costs.
But what do I know?