Enjoy the object before the label
Estate jewelry generally signals previous ownership; it does not, by itself, establish a particular age or period. Ask the seller what they mean by antique, vintage or period, and what evidence supports the description. Look at the actual craftsmanship instead of relying on a romantic category name.
Ask about changes
A piece may have been resized, repaired, polished or assembled using elements from more than one period. Those changes need not remove its appeal, but they should be explained. Request a condition description and, for a significant purchase, consider an independent assessment suited to that object.
Think about wearability
Try the piece on if possible. Check the clasp, fit, balance and any details likely to catch on clothing. Ask whether the setting and any companion gems require special care. The right jewel should suit how you intend to use it, not only how it looks in a catalogue photograph.
Read the transaction terms
Clarify returns, any authenticity representations and the documentation provided. Retain the receipt and the seller’s description. A beautiful older piece can offer texture and personality, but its price should not be taken as a promise of future resale value.