1928 "PLEASE RETURN COVER...OFFICIAL INQUIRY" LABEL. 1928 large window envelope (230 x 102) from Waltham Cross, Herts with embossed KGV 1½d postal stationery which is uninked (albino), alongside WALTHAM CROSS date stamp 13 AU 28. On front fine and scarce label "Please return the cover of this letter for the purpose of an Official inquiry.." Presumably label affixed due to the unprinted image which necessitated G.P.O. inquiry. Very unusual. (Ref 93979).