Although it is a timepiece and not a jewelry piece per se, I think the iconic Cartier Tank watch, which was created in 1917 (and first offered for sale in 1922) is an example of the Art Deco style, in its bold, geometric, and modern form.
A good place to see beautiful examples of Art Deco jewelry is the Christies website. Just search there past lots and there are many breathtaking examples of Art Deco jewelry.
Here is a link to a Christies Art Deco jewelry search:
http://www.christies.com/LotFinder/searchresults.aspx?toogle=p&entry=art+deco&action=search&sid=49509b94-3cbe-41d2-aab5-1d5a41eab153&searchtype=p#toogle=p&entry=art+deco&action=sort&sid=49509b94-3cbe-41d2-aab5-1d5a41eab153&searchtype=p&selectedids=7797&sortby=ehigh
A good place to see beautiful examples of Art Deco jewelry is the Christies website. Just search there past lots and there are many breathtaking examples of Art Deco jewelry.
Here is a link to a Christies Art Deco jewelry search:
http://www.christies.com/LotFinder/searchresults.aspx?toogle=p&entry=art+deco&action=search&sid=49509b94-3cbe-41d2-aab5-1d5a41eab153&searchtype=p#toogle=p&entry=art+deco&action=sort&sid=49509b94-3cbe-41d2-aab5-1d5a41eab153&searchtype=p&selectedids=7797&sortby=ehigh