This is a vintage round platter by Dorothy Thorpe.
Gamma Glass.
It has an iridescent quality.
Changes color depending on the lighting and the background.
On a black background it is gold.
On a white background it is purple.
Divided into 3 sections.
I have a matching round plate in another listing.
Measurements -
Length - 17 3/4"
Width - 10 3/4"
Height - 1"