Wear a little piece of ancient history. This appears to be a punt from an ancient Roman glass vessel or bottle. The tribal-looking silver and brass bezel is from Afganistan.  Well-oxidized, the green color of the glass is radiant in the light.
 
Size: 3.25" dia w/ bezel, 2.65" dia w/o bezel. 0.5" deep
Sealed silver metal back.
Weight: 3.15 ozs