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Well Thats a stone from a mine no longer open but typically the stones sold years ago had to be somewhat fast to be considered a high grade stones so I think it will be a faster stone but the seller would be the best one to ask.
The last line says Extra-Fein, which is a quality grade. The "official" german vendor still sells extra-fein and extra-extra stones. This is similar to standart(extra-fein) and selected(extra-extra). Just a little info . Looks very nice, by the way. I don´t think that someone can tell you the exact layer. Looks similar to some La Veinettes I´ve seen, though. If you really want to know what this stone is about, try to get in contact with belgischerbrocken.com, maybe Mr. Lindner can help you.
Old coticule grading systems usually referred to how fast the stone was, the faster the higher the grade. Old rock coticules have lines on their surface and are freakishly fast but polish very nice edges as wellwhich is why they are top of the grading list.
I got the stone, and it is nicer looking than on the pics The color is a creamy yellow, 2/3 of the stone has holographic striations, and two holographic lines running lenghtwise on the hone. I tried it only once now, but it seems fast on slurry, but I couldn't get clear water dark so far. The surface is like glass, the honing feel is a very nice draw with water, and a faint draw with water, the feedback is good even for my newbie hands