1879 (Dec 1) 2d Mulready envelope, stereo a195, sent within London and cancelled by London “WC5” duplex, incorrectly surcharged “2d” postage due as the Mulready prepaid postage up to 4oz, so the recipient wrote to the Post Office pointing out that error and the P.O. officially responded with a O.H.M.S. G.P.O. printed entire (included) agreeing that the postage due was “erroneously charged” and stated that instructions have been giben to refund the twopence owed to him, a unique item regarding the late use of a Mulready and ideal for the final page of a Mulready exhibit.