I got an old IBM desktop computer to use in the shack, and when I opened
it up I found it has an RFID feature.

Of course I will disconnect the thing, but, just out of curiosity, what
frequency do these things work on? (I understand that RFID tags can be
either active or passive, but this one presumably is active, since it
has an antenna that plugs into the mobo. I have read that they all use
the same frequency, but each individual item has a unique code.)

Alan AB2OS