You’d think that armouries are one of the things that should be run by the book.
In Ft Benning (okay Moore) a lot of Arms Rooms are theoretically run by a Captain, as a tertiary duty that they have zero time in the day to actually oversea, the day to day operations are run by lower rank enlisted with maybe (key word maybe) an E-5 as the supervisor.
Hundreds of weapons go in and out for courses daily, and the Sig M17 (320) serialized part is just the trigger box.
Some Arms Rooms scan in/out with RFID tags, on a M4 that’s affixed to the lower (the serialized item) but there have been several different locations tried for the M17, none that I have seen actually are on the trigger box.
Many other schoolhouse guns are just logged in and out by rack #’s that are spray painted, or paint penned (or laser engraved in some units) on the weapons - usually the pistol grip for pistols (sometimes the slide) and buttstocks for carbines/rifles. The weekly, or course end 100% is supposed to check by S/N - but sometimes folks just check to see that racks are filled.
My guess is they got moved legitimately and incorrectly logged - but due to the nature of the Sig pistol if one wanted to scam the system you could fairly easily take the trigger box out and put the rest of the pistol away.
Theoretically everyone entering the vault signs in and out, and a pat down search is conducted when both entering and leaving.
Lots of theory - but in my experience rarely followed.