Constructed by Horst Seel and Gert Bender, 1974 to 1990.
Horst Seel competed in the 125cc World Championship from 1967 until 1977. He and Gert Bender built a a 125cc, water-cooled racer using a much-modified Maico engine for the 1974 season, achieving a 4th place at the German GP. In 1977 a crash in the Swedish GP ended his racing career, but the machines he built were campaigned by other riders. He later built a 12 cylinder two-stroke F1 engine which showed great potential but proved unreliable.
In the late 80s he built 80cc and 125cc Seel machines which did well. His son Jörg Seel raced these until 1990. In the late 1990s his focus was improving the Honda RS125 and training younger riders.
Sources: Wikipedia ES, H&H Classic Auctions