unmounted mint Block of Four Guyana, overprint errors and varieties, 1981-84, collection of approximately 400 mint stamps, vast majority in blocks or plate no. blocks of four, incl. Gibbons nos. 769Aa, 841b, 841c, 841d, 843a, 983cc, 1002a, 1003a, 1004a (two), O22a, OP3, OP4, OP5 (three), also incl. nine overprint varieties unlisted in Gibbons, never hinged, very fine, Gibbons £5,050+