I'm a retired lithographer, so those represent some nice "litho history" to me. I never worked with litho stones, because I began working in the lithographic trade much after those were used. However, I did do some work with zinc, litho plates upon which I drew with a wax-ey crayon. That was in a "General Graphic Arts" class I took in college. Litho stones are fascinating, because of their incredibly smooth surface, and the skill that was involved in the application of the litho ink to them by highly-skilled artisans. Keep in mind that the application to the litho stone had to be REVERSED, because this was a form of DIRECT lithography, as compared to the "offset lithography" that we have today, in which the plate is right-reading, the impression on the "offset blanket" is reversed, and then......THAT image (ink) is transferred to the paper.