15L9, D.O. Blood & Co., Philadelphia, PA, 1846 (2c) Black, full square margins, tied by blue "Baltimore Md. Apr 21" datestamp on cover to Alexandria, DC, manuscript "Way 5", stamp with light creases at top, very fine, this stamp is very rare tied on cover with this being one of the most desirable examples, 2022 Philatelic Foundation certificate (Scott $1,500) Provenance: Alfred H. Caspary (H.R. Harmer Sale 1071, 1957)