being a contraction of Dopyera Brothers' and also meaning "good" in their native Slovak language. Dobro released a competing resonator guitar with a single resonator with its concave surface uppermost, often described as bowl-shaped, under a distinctive circular perforated metal cover plate with the bridge at its center resting on an eight-legged aluminum spider. This system was cheaper to produce, and produced more volume than National's tricone. Over time, the word "dobro" has become a genericized trademark used to refer to any resonator guitar. National biscuit National countered the Dobro with its own single resonator model, which Dopyera had designed before he left the company. They also continued to produce the tricone design, which many players preferred for its tone. Both National single and tricone resonators remained conical, with their convex surfaces uppermost. Single resonator models used a wooden biscuit at the cone apex to support the bridge. At this point, both companies sourced many components from Adolph Rickenbacker, including the aluminum resonators. National Dobro, Hound Dog, and Gibson After much legal action, the Dopyera brothers gained control of both National and Dobro in 1932, and subsequently merged them into the "National Dobro Corporation". However, they ceased all resonator guitars production following the U.S. entry into World War II in 1941. Emile Dopyera (also known as Ed Dopera) manufactured Dobros from 1959, before selling the company and trademark to Semie Moseley, who merged it with his Mosrite guitar company and manufactured Dobros for a time. In 1967, Rudy and Emile Dopyera formed the Original Musical Instrument Company (OMI) to manufacture resonator guitars, first branded Hound Dog. In 1970 they again acquired the Dobro trademark, Mosrite having gone into temporary liquidation. The Gibson Guitar Corporation acquired OMI in 1993, and announced it would defend its right to exclusive use of the Dobro trademark—which many people commonly used for any resonator guitar. , Gibson produces several round sound hole models under the Dobro name, and cheaper f-hole models both under the Hound Dog name and also its Epiphone brand. All have a single resonator, and many are available in either round or square neck. Other National instruments After the formation of the National Dobro Corporation, the term National was often used to refer to an instrument with a non-inverted cone, to distinguish these designs from the inverted-cone Dobro. Makers particularly used it for single-cone biscuit designs, as the relatively elaborate and expensive