Does anyone know the original maker of an antique ring with the stamp p.s.co. on the band?

Question

It's a 14k gold band, with what looks like a large square sapphire surrounded by smaller sapphires.

Answer 1

HERE'S A PIC OF IT

http://www.goantiques.com/scripts/images,id,1011121.html

PSCO© (Plainville Stock Company) is a quite famous jewelry maker and has been going since 1872.

Answer 2

I think is the mark for Plainville Stock Co., a 30s jewelry maker.