The finest known example of the 1922 Kenya and Uganda £10 Green & Black was the top selling stamp of Robert A Siegel's Worldwide Stamps and Postal History auction, held on April 16-17 in New York.

Bearing a profile portrait of the British king George V, the stamp made an outstanding 52.9% increase on its $17,000 pre-sale valuation, selling for $26,000.

"Almost certainly" the finest copy of this rare watermark variety

The £10 Green & Black is a watermark variety, with this example showing the watermark crown to the right of "CA". It is extremely fine, described by the auction house as "a phenomenal mint never-hinged example…almost certainly the finest copy."

The 2p and 4p stamps were never issued

Also selling well was a rare set of the 1907 2p Violet and 4p Black and Gray Green from the British Central Africa King Edward VII issue, each of which remains in sound condition.

Considered to be the rarest of all British Commonwealth King Edward VII issues, there are thought to be only 12 examples of each stamp extant in private hands.

The 2p and 4p stamps of British Central Africa were prepared but never issued, with the name of the territory changed to Nyasaland Protectorate in July 6, 1907. It is thought that only 18 examples of each reached the market, with a block of four and a single of each in the Royal Collection, and a further single of each in the British Library.

Paul Fraser Collectibles has some of the finest stamps from Great Britain and the British Commonwealth for sale, including unique examples such as The Black Empress and the largest block of Penny Black's from plate three in private hands.