One of the rarest of the US' bluish paper stamps, the 1909 Washington 4c, has sold at the top of Regency Superior's November 23-24 sale as official auctioneer of Chicagopex 2013.

The bluish paper series of stamps were created in 1909 when the post office began experimenting with including rag content into the paper mix, which gave it a bluish colour

Selling at the annual meeting of the Chicago Philatelic Society, the stamp made $21,000. It is one of just 100 or less known to exist and a strong example, showing full original gum, lightly hinged with nice centring.

Also selling was a fine centre line block of four of the 1908 Lincoln 5c blue imperf, which is one of less than six examples known to exist. This example has been graded PSE XF 90, with the bottom two stamps never hinged and the top two lightly hinged. It made $12,000.

Paul Fraser Collectibles has a superb selection of rare stamps for sale.