City letter carrier cap badge, number 518
U.S. Post Office Department City Delivery Service cap badge, number 518, with eyelet and cross pin on verso. Spread eagle supporting U.S. shield surmounts elliptical medallion with upper portion marked "U.S. POST OFFICE" and lower portion "PHILADELPHIA, PA" in japanned raised block letters.
Shown is a service badge that met department specifications and was worn by a Philadelphia, Pennsylvania, letter carrier after 1922. The badge is made of German silver, a metallic element containing copper, zinc, and nickel. The Post Office Department chose this metal because of its hardness and resistance to corrosion, an important consideration since the letter carrier's work constantly exposed the badge to harsh and fluctuating weather conditions.