This copper fairy lantern -or fishermen lights... cage, etc.- has as "stone of choice" an old glass beach combed piece from Guantanamo Bay. I know a lady that was living in the base and used to spend her time walking  on the beach collecting wonders like this. 
Thick and bold, it is Old glass, washed who knows from where and when... certainly not "man made" -tumbled glass- and not new glass. 
Large, it measures total 93x30mm approx.