Such a ring is known from the European Patent Application No. 1,132,017, the ring having a detent mechanism, on one hand, and the ring parts being provided with retention means, on the other hand.
Furthermore, rings are known where parts are mutually displaceable or can be lifted off. As early as in the Middle Ages and later, rings having displaceable or removable or openable parts have existed, thereby allowing either to change the ring and to reveal other aspects or to keep small objects.