Original oil and gas trade magazine vintage ad for THE AMERICAN HAMMERED PISTON. RING COMPANY. Main office and factory was located in Baltimore, MD. Individually Cast, mechanically Hammered to Give Lasting Tension, Particularly Designed and Adapted for Oil Field and Other Severe Service. Artwork is signed "OFM", probably by the artist Othello Francis Michetti. Unique 1928 old petroleum oilfield industry equipment magazine advertisement