Dating a vintage necklace by its clasp is not a straightforward task.The spring ring clasp, for instance, was developed back in the 1840s.As mentioned above, these elements include style, material and maker’s marks, if any.Just like true detective work, dating necklaces always requires piecing together several clues.Hallmarks are small markings stamped on gold, silver and platinum articles.A British Hallmark means that the article has been independently tested and guarantees that it conforms to all legal standards of purity (fineness).
The Hallmarking Act 1973 changed on 1 January 1999 and allows articles of higher and lower standards of fineness to be sold. Consumers may now choose from a much wider range of goods but to continue to benefit from the same level of protection. Using a British Hallmark Guide How to quickly identify gold and Silver hallmarks that you see in car boot sales and markets.
SHIEBLER & CO SHREVE, CRUMP & LOW SIMPSON, HALL, MILLER & CO TIFFANY & CO TOWLE TUTTLE SILVERSMITHS   WALLACE WATSON COMPANY E. WEBSTER & SON WHITING MFG CO WILCOX SILVER PLATE CO AMERICAN STERLING SILVER MARKS Aa / Am An / Az Ba / Bh Bi / Bz Ca / Cn Co / Cz Da / Dt Du / Dz E Fa / Fn Fo / Fz Ga / Gh Gi / Gz Ha / Hh Hi / Hz I-J K La / Lh Li / Lz M N O P - Q Ra / Rn Ro / Rz Sa / Sh Si / Sz T - U - V Wa / WG Wh / Wz X - Y - Z This is a page of 'The What is?
Silver Dictionary' of A Small Collection of Antique Silver and Objects of vertu, a 1500 pages richly illustrated website offering all you need to know about antique silver, sterling silver, silverplate, Sheffield plate, electroplate silver, silverware, flatware, tea services and tea complements, marks and hallmarks, articles, books, auction catalogs, famous silversmiths (Tiffany, Gorham, Jensen, Elkington), history, oddities ...
After a short time, you will get a feel for what clasp styles were most popular in that era.
Knowledge of clasp types and the time periods in which they have been the most popular can help you verify the approximate age of a vintage necklace you might come across later on.
Unfortunately, you can’t always date a vintage necklace by its clasp alone.