Adams' City Express Post, 1850-51, 1¢ black on gray. O.g., full margins, staining caused by original gum on this thin pelure type paper, Fine appearance, still a very rare mint original gum stamp, listed but unpriced in Scott; with 2000 P.F. certificate. Scott No. 2L3  Estimate $750 - 1,000. $0 (Image)