Original stone trade vintage catalog for NATURAL SLATE BLACKBOARD COMPANY, was located in Pen Argyl, PA. Manufacturers of Pyramid Natural Slate Backboards. Ideal for writing surface. Installed in schools. One of the least absorptive of nature's products. Will not warp under repeated cleanings. Unbound from a large 1938 architectural catalog, this unique old one page technical brochure would display fantastic matted and framed. Nice graphics. A fabulous addition to your retro stone library.