Auction #93 Worldwide Air Post stamps and postal history, Zeppelin Flight items, philatelic rarities of the World

1961, Helicopter over the Kremlin, black surcharge 6k on 60k ultramarine, horizontal pair, right stamp without ''6'' variety of surcharge (positions 19-20 of 80-stamp sheet), full OG, left stamp has somewhat gum foxing in places, right one (error) is completely all right, NH, VF and scarce error, which occurs in a small part of print run only, N. Mandrovski certificate, Est. $1,200-$1,500