A set of 12 transparent colored Lucite acrylic plastic Glo Star 5-point star reflectors for C-7 type (standard bulb) Christmas light strings. They're about 2-3/4 inches diameter and look great when the tree is lit up. Each has an embossed patent number dating to 1949 around the center opening.
I'm including a bonus larger clear Glo Star that is nearly 5 inches across. It has some flakes along the bottom edges and a couple of melt mark lines. You can insert one of the smaller stars in the center for a double layered reflector or tree top, or use it alone with an outdoor C9 type bulb. The second photo shows an example of what the two sizes look like when put together on a light string.