1961 cover endorsed O.H.M.S. sent stampless with a ZARIA 23 NO 61 cancellation. The cover was taxed, probably because it contained a card or something that did not warrant the O.H.M.S. privilege of free postage. A âTâ tax mark and a m/s â6dâ are on the cover which has had a 6d postage due affixed and tied by a Registered Zaria 2 12 61 cancel. Fine and very uncommon.