An 1854-1857 watermark large crown block of 12 is to star in an auction at Spink London.
The two pence blue block features perforated edges
The lot is expected to make £12,000-15,000 ($18,460-23,075) at the November 27 sale of Great British Stamps and Postal History.
The issue was among the first to utilise perforation as a method of separating individual stamps. Prior to that, they were laboriously cut by hand.
The present lot displays much of its original gum, with five of the stamps in unmounted mint condition.
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