U.S. Scott 815 (2) Prexies on cover making a convenience overpayment of the 5 cent air mail rate and 13 cent special delivery fee by 2 cents. The envelope was mailed from San Francisco, California to Denver, Colorado on September 25, 1947. The advertising corner card is for the Walcrest Corporation in San Francisco and says Walcrest is "WATERPROOF" and "VALUBILT" in a possible reference to a wall safe.