Natural pearl?

by Sandy
(Salt Springs, Florida USA)

I think I have a "gold glow" natural pearl ring, but I really have no idea, it looks like it has a "soul". (Corny, but the best way I can describe it) - It is set in an "old fashioned" setting. It is marked sterling silver with an arrow pointing to the right, then a Capital "U", then another arrow pointing to the left. It's quite large.

Who would I contact to get it ex-rayed and about how much would it cost? I am currently unable to include a picture, but will when my son comes home to visit! :)
Thanks Sandy