This item is 13/16" with a flat reverse which has mother of pearl rainbow coloration plus a mounted piece of brass that has an extending pair of oval studs. The front of the piece is domed. The image, with no dot pattern, is on a thin layer of glossy substance which coated the underlying mother of pearl surface. There is some tiny loss of this coating but primarily from the outer edges with just a few tiny dots of detail missing from the incredibly sharply detailed Lincoln portrait. Most likely the piece is from the 1890s or perhaps as late as his birth centennial in 1909 but it is quite fascinating and also the only example we have seen.