I am wondering if it may be made from a bead broken in half. Would be a great way to preserve it. Imagine the bead was broken in half, and then cold worked, and drilled. The size of the hole is inconsistent with the size of the holes of the round beads made with this technique and in this period. When you look at the hole, it goes straight through the mosaic, instead of the mosaic being plces around it, which would have been done in a hot technique on a mandrel. Also, the neck of the turtle shows the inner layer of the bead, which has no mosaic on it. To me, it looks like it was ground down to make the indentation.

Either way: very cool.