I just bought a "gold" ring that was advertised as 10K gold but upon receipt I find that the mark is not exactly 10K. It has what looks to be a capital U with what looks to be an arrow passing horizontally through it from left to right, but the arrow tip is not visible, only the arrow "tail", It is then followed by 10.

Sounds like it's not even gold.

I would get it acid-checked by a reputable jeweler.

Get it checked immediately.

Researching Costume Jewelry History, Companies and Signatures (http://www.illusionjewels.com/costumejewelrymarksu.html)

Scroll down until you see the U and Arrow.

http://imageevent.com/publicgallery/miscellaneous/uncasjewelry000

http://www.jltimelessjewelry.com/uncas-manufacturing.html