I was thrilled to find a mid century Royal Copenhagen glaze test plate in shades of blue this summer--and equally thrilled to find this unmarked French one, in autumnal shades of brown and orange, this week in Maine, feeling just right for the season. I've kept an eye out for these for years, and pretty much never come across them; they are scarce things, made for internal use at the studio or factory, to test and serve as reference for the specific colors produced by a spectrum of glazes. At the center of the face of the plate appears "Orange-Brun" and "Serie 11-12" on the reverse, indicating that this was one of a series of test plates surely covering a full rainbow spectrum, with each shade on the face of the plate individually numbered. If only I had them all! 

10 3/4" in diameter. Excellent condition, pretty much completely perfect, bright white with rich color.