Silver plated (?) ring

[Skamaniac]

I dug up a shallow silver colored ring the other day. Inside it says what I think is "GD 925." It might be "CO" or "CD," it's hard to tell.

I know about the SP or EP marks for silver plating, but does anyone know what this mark means?

I will try to attach a photo tomorrow, but perhaps someone knows without even seeing the mark.