50 Francs, 1944, SS Field Post, Volunteer Associations of the Flemish Legion, For Airmail, black ultramarine / ultramarine, small block of 2 x 2 stamps, as issued, mint never hinged, flawless condition, unsigned, with very rare partial perforation, only two horizontal rows of linear perforation applied, in Michel, only the variants printed on the back, without gum, with partial perforations are known, not listed in Michel.