A British 1862 3p rose will lead an online auction at Robert A Siegel with a £40,000 ($67,300) estimate.
The auction will run on May 14-15 and features a range of world stamps alongside a number of classic British issues.
The 3p rose offered is taken from a sheet of test printings that were submitted for approval.
After they were signed off, the sheet was perforated and sold alongside the regular issue, but the plate was never reused.
This is one of only five specimens from test plate three known to exist. It is unused, without gum, and displays partial reperforations at the borders - which are common with stamps of this kind.
A British 1902 five shilling carmine rose IR Official stamp is valued at £36,500 ($61,411).
The lot has been expertly repaired and regummed, displaying rich colour and a strong impression. It's one of a large number of high value stamps set aside for internal use by the Inland Revenue - hence the overprint.
A recent sale at Spink London saw an 1884-1888 £1 brown-lilac IR Official auction for £45,000 ($75,217).
We have a strong collection of stamps available including this superb used £5 Orange, which carries a 1901 datestamp.
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