10 November 1970, Netherlands
design: William Graatsma & Jan Slothouber
Slothouber and Graatsma were a design/architectural unit which formed the Centre for Cubic Constructions (CCC) in Heerlen and made a Dutch presentation at the Venice Biennial in 1970. Their creations were always related to cubes – thus their retrospective exhibition was named Cubics. More images from the show and the set of stamps are shown in this link.
One of my best favourite stamps of all time and I wonder why I have not featured it in this blog until now!