MAX: The third one [ring] is from the twenties … Large diamond in the middle …Diamond clusters on the sides … A little Deco.
Max is referring to Art Deco, a decorative style which flourished in the 1920s and influenced the style of architecture, furniture, jewellery, fashion, vehicles, and everyday objects. Art Deco was designed to be both modern and luxurious, with extravagent yet exquisite craftsmanship.
Art Deco jewellery is usually white-gold or platinum, with European-cut diamonds, filigree work, and geometric designs.
The Annotated Gilmore Girls 