Genuine, triple fine, Rottenstone powder. The same that’s been used by professional stock finishers for generations. Mix with linseed oil; becomes a fast, but fine-cutting abrasive that’s easily worked over the finish with a felt pad. Use on fully dried finishes only.
Big Book Catalog, Issue:69, Page:421
SPECS: 3F grade. Plastic jar. 8 oz. (227 g) and 1 lb. (454 g).