Featured (silver) pendant with large pearl - where from?

I know next to nothing about pearls - but realize this is kind of a large one - the pearl itself is 16mm across. It's almost dome shaped, but the back side of the pearl is slightly convex and irregular, not flat. I think it's a real pearl based on all the reading I've done and the tooth test. The luster is really pretty. The bail of the pendant is marked only "925" - on the inside surface, the pendant itself I can't find a mark on. Here's some pics - any ideas where from?

Thanks for looking!

 

Possibly shell, but I don't think pearl.

 

Thanks, yes I guess it could be a piece of polished shell but I've never seen shell with that much luster before but it could very well be.

 

Looks like a Mabe pearl.
https://www.mastoloni.com/education/mabe-pearls/

 

I agree, a Mabe pearl. The pendant looks Indonesian.
Many white Mabe pearls are cultivated (saltwater) around the island of Lombok, Indonesia.

 

agree , Mabe......i bought Mon earrings for her birthday...similar..

 

Thank you very much everyone! Seems like there's a consensus that it's probably mabe.