These necklaces are made from plastic. The backs pop out of them so that you can place the character medallions into them. Currently I own two styles, the bow similar to the Scouts broaches, and a heart similar to Sailor Moons broach. There are several doubles of the medallions because I owned the bow style before purchasing the heart.
Although I paid $10 for these, they were originally found in dollar stores with the dark blue packaging. The copyright information can be found on the medallions photographs.