1928. Registered cover to an address in wARSAW, bearing WARZAVA 1928 FIRST Polish muniature sheet, isued for the Warsaw Philatelic Exhibition, postmarked with two strikes of ”SAMBOR c 7.V.1928”, an additional strike alongside and provisional boxed ”R” struck in the lower margin of the sheet, light vertical crease clear of the sheet at left, back flap missing, nevertheless an rare item.