BIAFRA 1969 (VARIETY) 4D INDEPENDENCE ANNIVERSARY IMPERF PROOF BLOCK WITH DOUBLE BLACK
4d Independence Anniversary imperforate proof block x 4 missing yellow (resulting in a magenta rather than orange frame) and instead printed with several down-shifted colours from the 1s value, including cyan and black. An extraordinary piece. Fresh and fine. Mint never hinged. SG36var; SC23var
