I bought it at a thrift store for $7.99
I think it's old-ish. It's handmade, I can tell by all the dingy marks and the fact that it's not totally symmetrical. It says sterling on the inside. These days they usually say 925 and not sterling.
I'm kind of leaning towards feashwater as a guess since most of the mabe pearls seem to be, but I thought I'd ask you guys what you think.