It looks like it was used to "penny" an old style screw in fuse. If people blew a fuse and didn't have a new one they would slip a penny behind the bad fuse and tighten it down to get the power back on. Some of these old style electrical panels are still in use today.
Check out my counterstamped
Lincoln Cent collection:
http://goccf.com/t/303507
Edited by chafemasterj
04/16/2019 08:30 am