This old Ohio Bell cable marker is a gem. These appeared for sale at one of the NIA National shows in the 1980s. I don't recall who the seller was. I believe these were used on a cement post to mark the location of splices and other important cable points. I have seen a much simpler version (not bell shaped) in a curb in West Palm Beach, FL. This one measures 4 1/2" from clapper to hanger.