Crown Jewels with Overlay and Lock Charms, Slave Version

Crown Jewels Necklace or Collar, orientation for usage depends on how it's made. (Dominant, Switchable, or Slave)

Dominant has no attachment points, Switchable has a D-Ring for possible attachment near the buckle in back, and slave will have an attachment point in front. That might be number of things including: a Drop Ring, D Ring, O-ring, Post with a small D ring, buried D Ring under the front edge, etc. 

It's shown here in the slave version.