What does it mean when jewelry has TFJ stamped on it?

Answer 1

 It is for the women's fraternity Alpha Xi Delta. It is taken to mean "Thanks for Joining". However, unless a member, you will never know what it actually means.

Answer 2

'TFJ' could mean a lot of things. It's hard to say with the information you have provided. However, I doubt if the marking has any technical importance with regards to the quality of the ring. My guess is that it's probably just a hallmark, made by the jeweler for the sake of identification.

Nathan Leon
http://www.b2cjewels.com