This rigid plastic choker is suitable to wear as is or you can hang charms in the open circles.....easy to do with links if you choose to do so. The "circle" is on the smaller side although the plastic opening expands. The diameter of the "circle" is 5 inches across. This was probably a children's jewelry item.
I have 4 other pictured colors listed separately. Just search "color" "plastic choker" in my store.
These chokers were made in Western Germany.