WSK motorcycle from 1957, manufactured by Wytwórnia Sprzętu Komunikacyjnego (WSK) in Świdnik, in 1957 renamed to PZL-Świdnik (it's a big Polish aerospace factory specializing in helicopters). This model is a twin brother of WFM M06 from Warsaw Motorcycle Factory. Świdnik was charged with this task, because Warsaw factory wasn't able to build sufficient number of motorcycles. The first WSK motorcycles were assembled in September 1954. Mass production in Świdnik started in 1955, a few month later then in Warsaw. Both motorcycles, WSK and WFM, were powered by the same S-01 engine. By 1957 all modernizations and changes were done simultaneously, and the only real difference between both machines was the logo. In 1958 Świdnik engineers suggested first individual changes. The prototype of WSK M06-Z was presented, with improved front suspension and better brakes, frame welded from closed rectangular sections (not C-shaped), deeper mudguards and more comfortable seat. Introducing all changes at once was expensive, that's why in February 1959 two models appeared: more expensive M06-Z (the most luxury version with chrome rims was priced 10600 zloty) and cheaper M06-L (7000 zloty) with modernized frame, seat and engine; the old S-01 engine was replaced with its successor, S-017, with power output of 6 HP. Next WSK model was M06-Z-150 with bigger (148cc) engine, and in 1964 WSK M06-64 was introduced, which was superior to products of Warsaw factory. WSK motorcycles were continued to October 1985, when the factory was closed. The overall production of WSK motorycles was about 2 000 000 units, over 1 700 000 of them belonging to 125cc class.