I wonder if the "shells" could also be made from the same material?
Its just that I spotted this absolutely huge and extremely heavy waste-paper bin(?) earlier today and nabbed it. Its modern, but made from some type of clear resin. The fish, and especially the seaweed, look as though they too are made of plastic. The seaweed in particular is 3-dimensional, and along with the fish, which are thinner, appear to be encased in the clear resin. I'm not sure whether the container is double walled, and the decoration has been placed inside a cavity, or whether the wall is solid resin with the decoration suspended in it.
Now I probably wouldn't have bought it if it wasn't for your lovely brooch, so its your fault Rose
However, your brooch wins hands down