This one's a no-brainer. When buying vintage jewelry, as with any designer piece, you've got to look for a few important markings. This includes any logos and writing on the outside or inside of the piece. Knowledge of the brand's signature will be useful, but just basic common sense is enough. Obviously if "Versace" looks more like "Vorsace" the jewelry isn't authentic. Make sure you look out for the small details because counterfeiters are getting better at making these less noticeable.
3. Look For Signature Markings