The BWM engines were a relatively short-lived range of high-quality model engines manufactured in West Berlin during the Cold War period when the Berlin Wall was very much in place. Manufacture began in 1952, being continued until 1957.
The most prominent member of the range was the crankshaft front rotary valve BWM 250D diesel of 2.47 cc displacement. This engine was a very dependable performer, developing around 0.23 BHP @ 11,500 rpm - a quite reasonable figure for a plain bearing sports diesel of the period. There was also a rear disc valve 2.5 cc model called the BWM 251 which developed a claimed 0.27 BHP @ 15,000 rpm. This model did not survive the 1954 takeover of the range by the former BWM works manager Manfred Göcking, consequently being very rare today. A number of other models also joined the range for brief periods.
The full story of the BWM range can be found on Ron Chernich's "Model Engine News" (MEN) web-site.