they appear 2b MANUAL doorbell/chimes...
with a slot for name/owner (in the R example)
all the rage in da'60s...
on HOUSES n trailerz...
rotate the knob and DING DONG!
IF those were mounted on the stream,
look for a corroded, indented matching shape
near the entry door.
hopefully the evidence has been erased.
all of the true things that i am about to tell you are shameless lies. l.b.j.
we are here on earth to fart around. don't let anybody tell you any different. k.v.