Vintage sterling silver purple / violet square / princess cut crystal riviere necklace - Art Deco or possibly earlier (Edwardian or 1920s). Lovely sized sparkling light purple crystal rhinestones, bezel set in lovely open-backed sterling silver raised settings, connected by sterling silver double links. The necklace has a length of up to 16 inches, and is adjustable using the secure spring ring clasp and length of extension chain.

The two settings on either side of the push-in clasp are stamped - in this case both with 'PAT 311897'. Usually, there is one patent stamp like this, then a sterling silver stamp on the other end (see links to other examples below). So this necklace has been tested and confirmed as sterling silver. 

This patent was granted on 23rd May 1929 to a jeweller called Walter Henry Collins. The last picture shows the patent drawings and how the construction was achieved.

I have other versions with different types and colours of stone available on my website. This necklace is in very good vintage condition.