Sorry about that, sir...if it’s any consolation, I was almost booted from the public library a few minutes ago for having distracting hair.
The only mark that shows inside the case back is 1339, and it is no help in determining whether the case is karat gold, or otherwise. Please tell us what other marks there might be on the case. (i e : .585, .750, 9 karat, 14 karat, 18 karat), or something else.
This is my favorite of the 60th anniversary editions. Just got it last night, and I am quite happy with the decision.