The original design for the "Mystery Set" single-colour "Boule" rings was patented in 1935 and has become an all-time classic. The two-coloured version dates from the 1950s. They are always admired and often imitated. Only Van Cleef & Arpels, however, produce jewels of such skillfulness that, in this instance, the "Mystery Setting" features asymmetrical stones, so that every stone has its unique place in the design.