Starting in 1960, Fablok built a small three-axle diesel locomotive for narrow gauge railways that was called WLs150. The number stood for the number of horsepower available, which came from a five-cylinder diesel engine. By 1969, a total of 144 had been built for gauges of 750, 785 and 900 mm, 33 of which had been delivered to PKP. In the same year, Zastal started production of the WLs180 with a 180 hp six-cylinder. 47 were built, of which three went to PKP. PKP called both variants Lyd1, what stood for diesel, three axles, high-pressure combustion and mechanical gearbox. 