Udo Krell applied for German patent 3138663 for his puzzle mechanism in September 1981. Several inventors had proposed mechanisms for the 5x5x5 cube, but it was Krell's design which was first manufactured (by Uwe Mèffert) in Hong Kong. It was marketed by Ideal Toys in 1983 in Germany as "Rubik's Wahn" (Wahn = delusion or illusion).
Péter Sebestény, the inventor of the 4x4x4 Cube, later remarked that "I didn't know at that time and learned only years later that Mr. Udo Krell, the inventor lived in Hamburg, in the same city as I did. Naturally, Ideal Toy gave me no hint that the 5x5x5 was being developed."