Created for only two years between 1957 and 1959, an unknown quantity of these were painted with his signature International Klein Blue.

These are essentially small Yves Klein paintings. But, they’re so much more. Since these weren’t officially issued stamps, Klein had to go to great lengths to get them accepted as postage, including bribing carriers to stamp them, marking them as valid postage. Each mark was validation of the concept.

Co-opting the government in this act was undoubtedly subversive and pre-dates similar acts of mail art and Fluxus.

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