Identifying possible French gold hallmark and maker's mark on a ring

by James Bennett
(San Clemente, California)

These are photos of a gold ring showing what appears to be a hallmark of an Eagle's Head in one photo, and in the other photo, a possible maker's mark that seems to appear as follows:

first line: 18K (printed upside down )
second line: the letter "C";three bars; and then
the letter "D"
third line: the letter "R"

I believe that the Eagle's Head is a French hallmark that was used from circa. 1838 to ?, that indicates 18K Gold.

My questions are:
Am I correct about the hallmark, and if so, how long was it in use?
Can you identify the other markings, and tell me what they represent?

I thank you for your time and consideration.