#7, 1c Blue Type II, Precancelled and Tied by Philadelphia Carrier Double-Oval on Drop Letter to P.O. Box

1c Blue Type II with ample margins to just in at top, tied by “U.S.P.O. Despatch / Pre-Paid / One Cent” double-oval carrier marking on buff cover addressed to a Philadelphia post office box. The stamp was precancelled and used to prepay the 1c carrier fee to prevent the stamps from being used for regular postage and to prevent accounting problems for the post office and carrier department. A fascinating postal artifact.