GC Maker's Mark

Hello,

I have a vintage gold ring (belonged to my grandfather) that has no markings other than what looks to be the letters GC that are inside of a diamond shape.

The ring itself has a flat face with worn script initials on it (not even sure if they are his!) and both sides of the ring has what looks to be - victorian scroll work.

My dilemma is that the ring is broken in half, and the local jewelers wants $35 just to let me know if it's gold or not. I'd love to have it fixed and wear it, but the cost to do so seems prohibitive if it's not even gold.

I understand that it's carat is impossible to determine without testing, but I was curious if the mark itself could possibly give a tell tale sign.

Thanks so much for your thoughts

Tom