Hi Rosanna,
It is a unique one. IÕve never seen such a bead.
But the color green occurs in beads from the Krobo area. Also the use of small beads as eyes as one of the eyes in your bead. There are also green Akoso beads. The shiny surface occurs too when the heat of the furnace is high enough and no grinding afterwards is used.
Added are two photographs of beads collected in Benin with a black core and shiny surface and just about the same size as yours. The only examples I have. But were in Africa they were made is an enigma to me.

Pity you did not call Amsterdam on your last trip, Hans

PS these two beads are also in the collection of the Picards on internet