Belgium, 1920 Olympic Set, Red "Specimen" Overprint. Blocks of 4, o.g., n.h., with red "Specimen" overprint and security punch from the archives of the American Bank Note Co., printers of the stamps. Scott No. B48-B50  Estimate $750 - 1,000. Specimens are distributed to various countries through the offices of the UPU for the purposes of identification. $0 (Image)