I have a new variation of the Beauclaire Rose mounted on a square frustra (google it!) of (probably) Lucite (a.k.a perspex, acrylic, etc).
The rose is made from metalised plastic with a loop of wire threaded through the shank and protruding from the Lucite.
General Plastics made good use of this rose design, producing it in many variations of colour and material, as well as in combination with Lucite mounts like these.
Note that there are various clear plastics that are hard to tell apart. Some collectors don’t think it is worth bothering to try! Lucite can also be coloured, opaque, carved, painted, and have inclusions such as glitter and pearlshell chips.
This advert from a 1954 ‘Just Buttons’ magazine has Lucite mounts decorated with seashells.
Du Pont had licensed its version of this acrylic plastic in the 1930s ( see http://www.austbuttonhistory.com/its-un-australian/the-wide-world-of-materials/#Lucite ) however it was during WW2 that it really came into its own as a substitute for glass. Button manufacturers were able to fashion buttons from the large amount of scrap acrylic material left over from the manufacturer of airplane windows. It was able to be hand carved and polished, giving the appearance of crystal buttons but much lighter and less breakable. Lucite and perspex buttons were mentioned in the Australian press from 1940 onwards, the label changing to acrylic in the late 1950s.