unmounted mint Block Larger Than four ACP/PVAD: 30p. deep olive-grey variety part imperforate, a horizontal strip of five stamps (end stamp damaged at side) which are imperforate between stamps and margin plus partly at sides in an upper right corner block of ten showing progressive failure of the perforating machine, a horizontal crease between rows and tear between left pair on the lower row, unmounted mint and thought to be the only examples of this error. Photo