VINTAGE ADS
You can look for vintage advertisements in magazines and also catalogs to get a feel for the age of the piece and also to familiarize yourself with what was in style during that time period.
COPYRIGHTS
The copyright symbol on a piece of jewelry indicates a date of 1956 or later. In 1956 it became much more cost effective to register a design Copyright which led designers to abandoned the expensive patent registration process. From Penelope's Pearls
