I googled Arkerem West Germany and I think the West Germany part screwed up my search results.The word "Arkeram" was easily Googleable and Gamma turns out to be right. It's reconstituted arkie stone powder fired in a kiln. Couldn't find any grit ratings, but did see this:
The second type is a soft Arkansas stone called Arkeram, made from extra fine Arkansas stone powder that is molded into the desired shape then fired and bonded in a kiln. Soft Arkeram Arkansas stones have a faster cutting action but need to be dressed back into shape more often.
Thanks again, I think I'll just leave it in the closet for tools. It seems really fine but I'm not going to risk it with this info.