I see JR inside the circle too. It's upside down. If that is upside down maybe the silver content mark is also and it's 875 instead of c78?? SOrry I don't know maker's marks well enough to help id for you.
I hope I get the image correct! This appears to be a cut glass inside the sterling mountings with silver painted accents. Please help me id the maker and also the type of glass this is. http://img.photobucket.com/albums/v38/BallardTN/JEWELRY-MEXICAN/100_2255_mark.jpg http://img.photobucket.com/album...