Tiffany? Cartier? How to tell?

[evilmailjeep]

A friend of mine has a wedding band, that was his mom's...but it has been resized at least twice now, and has no marks of any kind in it...(It is yellow gold, with raised Roman numerals on the outside) Are there sources listing older styles of designer jewelry, and some sources that might be able to help in identification of old pieces?

[Snooper]

This isn't of much help I'm sure, but I've been told if you bring the piece to your local Tiff/Cartier they can verify it if it's authentic vs. a knock off.  That might help since the markings are gone...