Letter carriers donned this shapeless style of uniform jacket, also referred to as a "sack coat," on their daily rounds for city delivery service. Sewn on the interior is a manufacturer's label from the Penn Garment Company of Williamsport, Pennsylvania, in gold thread on a green ribbon. The single-breasted, blue-gray, woolen jacket has a slanted-flap breast pocket on the left and two flap pockets at the waist. Black braid accents the pocket flaps; the Post Office Department uniforms had black trim until 1956, when the color scheme was changed to maroon. The braid also extends up the front and around the collar and appears two inches above the cuff. The jacket fastens by five brass buttons featuring an imprint of a uniformed letter carrier in mid-stride above the letters “P.O.D.” for 'Post Office Department'. (The POD kept this style of buttons in circulation from 1893 to 1970.) Two brass buttons also decorate the cuff. Above this cuff’s black trim are two silver service stars, worn by letter carriers to connote thirty years of service. The POD introduced the color-coded service star patches in 1899 to replace the service stripes.
National Association of Letter Carriers. “Dressed for Success: The Evolution of Letter Carrier Uniforms.” Postal Record. October 1986.
http://blue.usps.gov/postalhistory/histuniforms.htm (Accessed June 6, 2002)