double circle datestamp duplexed with circle of wedges ties pair of 1861 3c Rose (65) to cover to Philadelphia, Pennsylvania, cornercard for "U.S. Sanitary Commission", faults along top edge, still fine strike, one of two recorded covers with the letter "U" datestamp (the other of which we recently sold in the Challenger Collection), Piszkiewicz believes this initial stands for "Union Station" and was quickly replaced by the letter "X"