RFD letter carrier cap badge
U.S. Post Office Department Rural Free Delivery (RFD) tiara-style cap badge with elongated head strap attachment hole on either end of insignia. "Martinsburg / W. Va." written in pencil on verso.
Many of the RFD designed badges, like the one shown, strapped around the letter carrier's hat or helmet. This helped prevent the badge from falling off while the carrier traveled down rugged country roads.