Never did geocaching but for a while back when I got my first hand held GPS around 2002 (yellow eTrex) I got into looking for geodedic survey markers, a lot of them have been destroyed over time but I did find maybe a half dozen of them.
Back when there weren’t too many geocaches, the geocaching folks decided to add survey markers as a ‘cache’-like goal that counted towards your stats. I’ve only found one – on Mount Baldy in Alaska.