The pair of vertically attached stamps of the Chinese revolutionary figure is particularly rare because of an error in which some of the stamp is printed upside down, including the $2 sign, Zurich Asia said in a press release.
The previous highest price for a Republic of China stamp was set in March when an inverted Sun Yat Sen stamp sold for HK$2.4 million, the auction house said.
(Frederik Balfour is a reporter-at-large for Muse, the arts and leisure section of Bloomberg News. Opinions expressed are his own.)
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