Nauru 1916–23 5s rose-carmine and 10s indigo-blue, Waterlow printing, with non-Universal Postal Union (U.P.U.) “SPECIMEN” overprint (type GB26), SG17/18s.
Matching lower right corner blocks of four with two sets of pencil initials in the corner margin, unmounted mint, with full original gum. Minor gum bends and one 10s with a small area of natural gum disturbance, otherwise in superb condition and wonderfully fresh.
A spectacular and unique pair of positional multiples from the sheets of 40 released by the British Postal Museum (BPMA) in 2014.
Last sold by Stanley Gibbons in 2016 for £12,500.
