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The SiM 2b was named after the Polish aviation weekly magazine "(S)krzydla (i) (M)otor" which appeared from 1946 to 1953 (in English this translates as "Wings and Motor"). Two versions of the engine exist: the SiM 2 and the SiM 2b. Both are now virtually unobtainable in Poland in any condition. The designer and manufacturer of the SiM engines was Mr. Michal Oldachowski from Warsaw (pronounced Me-how Alldukhovski). Manufacture was—just like in the case of Herr Benno Schlosser in the DDR—a private enterprise within the confines of the socialist economy.
References: 1000 Slow o modelarstwie. (1000 Words on Modelling) Wyd. MOM, Warszawa 1987 r. W.Schier.
Miniaturowe silniki spalinowe. (Miniature IC Engines). WKL, Warszawa 1976 r.
(Thanks to Arkadiusz Bugaj for this information)