Australia, 1891 Sydney O.H.M.S. Registered Envelope, 6d red entire posted locally to the Dept. of Public Instruction, with "Sydney, Ju 20, 91" duplex postmark and an unrecorded "Officially Registered, Sydney N.S.W., Ju 22, 91, 4d More to Pay" date stamp; minor staining, otherwise Very Fine, an extremely rare registration due marking. Estimate  $500 - 750. $0 (Image)