Thrift store find...

A friend of mine found this in a thrift store among a bunch of plastic junk jewelry...

Potch looks dark grey and not a true black (last pic). There is one side where it is thin and you can see through (best seen in 3rd pic, bottom left side) so no indication of a doublet.

Band is white gold. We think the two smaller accent stones on band might be diamonds.

What do you guys think? Is it the real deal and did he find the thrift of a lifetime? Can anyone identify where if might by from (we are thinking AUS but no clue which mine)? Either way I'm so envious cause he spent a total of 27 USD for it!