Wolfgang Seidel, of Germany, designed and built several custom radial engines. The ST540, ST770 and ST996 were among the smaller series of radial engines that were used in one-fifth scale and one-fourth-scale model aircraft. These engines varied in size from about 8 inches to 11 inches in diameter.
This pre-production model, built in the early 1980s, is one of his first prototypes intended to introduce his engines at trade fairs and model airplane shows and exhibitions. It is approximately 40cc (2.43 cubic inches) and closely resembles his first production engine; the small ST525 radial engine. It burns methanol on glow ignition and the rocker assemblies were manually lubricate before operation.