A mint 1923 1c green rotary sheet waste stamp is set to headline a sale at Kelleher Auctions on September 27-29.
The Flagship US, British and Worldwide Stamps and Postal History sale will be held in Danbury, Connecticut.
This is a very rare, never hinged specimen - one of approximately 20 in unused condition.
Rotary sheet waste stamps were produced between 1919 and 1923, using rotary presses.
They were initially discontinued when it emerged that the length and width of the stamps varied when compared with the standard flat press stamps.
The US Post Office wavered at first but went on to issue them anyway.
This example is a perf 11 specimen - so named for the 11 gauge perforator used to separate the stamps.
It's valued at $40,000-60,000.
A used example of the issue (one of only 13 survivors) sold for $90,000 in 2012.
A 1915 Marshall Islands G.R.I. 5s handstamp is valued at $35,000-50,000.
The British printed over the old stock of stamps when they captured the German held Marshall Islands in 1914. G.R.I. stands for George Rex Imperator (George King and Emperor).
The issue is popular with collectors due to its rarity, unusual history and attractive appearance. Another 5c specimen made £24,600 ($34,273) at Spink in 2014.
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