Most Antique and Estate pieces are, "one of kind" pieces.
Vintage jewelry almost always has a maker's mark somewhere on the piece.
Vintage pieces 1950's and prior, definitely check for some type of mark, such as small icon of the initials of the maker.
"Patina" is the word that dealers use for the sheen that occurs after years of use.
Vintage jewelry is sold in as-is condition as not to damage the gold, silver, or other
Vintage jewelry should show signs of wear, tarnish, dents, and lack of shine are all common earmarks of the real deal. If a piece looks like it's brand new, ask the dealer if it's been restored. Otherwise, simply assume that it's a really clever fake.
Inspect for Markings
Look for markings that indicate type of metal and purity.
Sterling Silver will be stamped .925 which is "92.5" percent silver
10 karat gold might have ".417" stamped on it.
14 karat gold might have ".585" stamped on it.
18 karat gold might have ".750" stamped on it.
Platinum will be marked "plat" as a stamp.
Sterling silver with gold plating will be marked, "Vermeil".
Antique Replica's and Costume Jewelry will not have authentic gem stones.
As always, cherish and enjoy your vintage jewelry!