The Jaskółka (Swallow) series of 2.5 cc model engines were manufactured in Poland from the mid 1950's to the early 1960's. They were designed by Stanislaw Górski, who remains probably Poland's best-remembered model engine designer. The Jaskółka engines and their 5 cc Sokól companions were produced to good standards, hence serving Polish modellers well. However, they were never seriously marketed in Western countries.
Although he is best known for his work with the Jaskółka range, Górski's activities extended well beyond that particular series. His story is one which richly deserves to be more widely appreciated than it has been in the past. I've attempted to redress this situation in a detailed article about Polish model engines and the work of Stanislaw Górski which may be found elsewhere on this website.