Well, the photos were taken by myself with the permission of the museum during one of my visits there. I#m not really sure if I'm allowed to post them here because they are not official, so maybe I should better remove them.
But maybe some more information of the museum and thuringian stones in general is interessting for you.
The slate museum in Steinach deals with the slate mining industry in this area. Hones and sharpening stones are only a smaller part of this industry, mainly slate school tables and slate pencils were produced and this area is very famous for that.
But in this museum there is one smaller room only dealing with hone stones.
Here you can see all kinds of hones, sharpening stones, sharpening wheels/discs and so on made of thuringian slate. And you find some history of the companies that were mining and trading this stones.
One interesting thing may be, that you don't see any Escher labeled stone there - nor any information about the Escher company.
One reason for that is, that the history about thuringian stones is much more than the history of Escher company.
Sharpening stones were mined in this area from the 14. century on in nearly all qualities and for all thinkable usages. There were coarse stones for sharpening scythe blades and very fine stones for razor or instrument honing and so on. Sharpening stones of this area were found in an ancient celtic city not far away, that exists more than 2200 years ago.
J.G. Escher arrived at the scenery, when he settled to Sonneberg around 1750. He first worked as a painter and then began to trade with slate products of this area.
So Escher was mainly a trading company who had his own mines but also bought stones from other mining companies in this area. This mining "companies" were mostly one/two man companies who had the right to mine in a certain area. For example in the year 1840 there were about 24 mines with 50 workers in total in the area of Steinach. Escher company itself was located in Sonneberg (there had been some mines in Sonneberg too, but most of the mines -even the ones for the recent known thuringian waterstones- had been in the area of Steinach). Escher brought the stones mainly mined in the Steinach area to Sonneberg, where they were labelled and selled around the world.
So - just a very short overview of Thuringian hone stone history - keep in mind that not only Escher-labelled stones are good thuringian hones. In Germany most of the Thuringians you find are not labelled. Mostly the hones were used by Barbers and even if the stones had been labelled once, no one who daily work with this tool kept any attention to a label that was bond on the back.