This sharpening stone is made with a special process...
According to iabrasive.com:
"Pacific Grinding Wheel Company
was established in Everett, Washington (U.S.A.) in 1898 as Pacific Emery Wheel Company by Mr. Anton Foss, Mr. Martin Johnson and Mr. P. Lee. Mr. Foss, who had the major interest, came from Norway.
opportunity, he established the business to supply grinding wheels to the lumbering industry for sharpening saws, planer knives, etc. The processes used for bonding the grinding wheels were the "Shellac" and "Silicate" processes"