The Celebrated Water Razor Hone

From a more courtly era when advertisers capitalized some nouns, referred to "cutlers" and used phrases like, "which will be sufficient to convince the most incredulous of their superiority."

Apparently made by a company called Escher, which quarried pure powder-like quartz embedded in chalk, resulting in fine, hard stones from 10,000 to 12,000 grit.  Generically they are referred to as   "Thuringian" stones, and are highly sought after by men who continue to prefer to shave with straight razors.