Yves Klein's blue pigment needs no introduction in his oeuvre.

Effectively an Yves Klein painting in miniature, this stamp is from a series that Klein first made in 1957 by painting blocks of blank stamps with what was to become his famous signature, the patented blue pigment officially registered as IKB, or International Klein Blue.

The blue stamps were created for mailing invitations to the opening of two pivotal exhibitions, in May 1957, at the Galerie Iris Clert Gallery and the Galerie Colette Allendy Gallery, both in Paris. The postal authorities were cajoled by Klein into accepting the stamps as if they were actual postage stamps printed by the French government, and they delivered all of the invitations.

Klein continued to use the stamps for two years following their 1957 introduction. This stamp is an unused, un-mailed example made by Klein between 1957 and 1959, perfect condition.