GRAY-BLACK-WHITE CUBE

GRAY-BLACK-WHITE CUBE. Cube made of a white plastic, gray plastic and black plastic slice without stickers. Made by myself in 1983 of standard cube, American cube and gray-plastic cube pieces.

My idea has been copied since and in 2007 one of these copies was sold at an online auction:

Phase: 9 Winning bid: $209
Notes: Unusual and refreshingly easy to solve. Pieces are either white, gray or black.