Welcome to Tnet.
Nice ring, but It’s not solid gold, I’m afraid.
The ‘R.G.P.' mark is for “Rolled Gold Plate”.
The maker mark with back-to-back C letters in triangles separated by an ampersand is for the Clark & Coombs Manufacturing Company, originally of North Attleboro, Massachusetts but later at New York City and Rhode Island. They began business c.1862 and used a variety of styles for the ampersand within the mark. That has led to confusion about possible dating, with some sources saying the ‘conventional’ ampersand was used until 1915 and then replaced by a more stylised one. I have become doubtful about that. First use of a ‘C&C’ mark is claimed in the trademark registration as 1923 and it was cancelled in 1988.
See a previous post here:
https://www.treasurenet.com/threads/markers-mark-on-a-large-sterling-ring.318644/#post-7167143