The stain is Mason 6020. The porcelain body, L3778D1. Manganese alumina stains are highly refractory, so much so that they severely affect degree-of-melting when added to glazes. They simply do not work in glazes. But in vitreous bodies, like this one, the stain has no effect on the degree of vitrification! And produces a color that is difficult to achieve in glazes.