Fine grit natural razor hones. Most famous perhaps being the Escher's. Smooth, matte colors that may contain grays, greens, blues, yellows, even browns. Most commonly gray or gray/green. Grit estimations are in the range of 10-15k. Commonly cut long and narrow, 5x1, 7x1, 7x1.5, 7x2, etc. Commonly labeled as "German water Hone", "German Razor Hone" or similarly. Often found in wooden boxes with a slurry stone. Many vintage stones have instructions indicating the stone is to be always used with slurry. Instructions typically warn against the use of oil. There are theories passed around forums on which colors are superior. The only citable mention known suggests that brown is the highest quality.