Original heating trade vintage catalog for ROYAL VENTILATOR COMPANY, was located at 417 Locust Street, Philadelphia, PA. Manufacturers of Ventilators. Products include Double Cone Damper, Glass Top, Rectangular & Square and Smoke Jack. Insect proof and Bird proof. Made of galvanized steel, copper, toncan metal, Armco or iron. Unbound from a large 1931 architectural catalog, this unique old one page technical brochure would display beautifully matted and framed. Nice graphics. A marvelous addition to your retro ventilation equipment library. Slight damp stain on outer edge.