Tony,
I just used the stone with a slurry. Definitely not a fast cutter, and feels smooth on the edge. I think I did over 70 laps and there was not much metal removed at all. So this leads me to think that it is not a Hunsrueck. Honestly, I think I would have liked a faster cutting stone than what it is How fast do the Hunsruecks cut? (comparatively) Lapped and with slurry, my stone looks very much like a regular Escher and I have the label that I have seen on the stones sold by Kees.

Eric,
I am pretty sure they aren't Manufactum Thuringens. Kees said they come from a small family operation, iirc

Pilot,
Kees sold a few under his ebay name Roos something something (number, including 0 and 6, iirc). Not an e-bay store. PM him here if interested, he is always very helpful.

Cheers
Ivo