10 C. Postal stamp ultramarine with overprint "fortress Lorient", variety "inverted overprint", corner margin piece lower left with sheet number "73926", unused with paper fiber attachments and tiny on gum side toned spot, in the lower margin a little separated, issued only 650 stamps - of it only a few with sheet number (approximate 6 - 7 are possible) known, extremely rare, photo expertize Lothar Herbst VP (2017)