With this superb machine, Marek Luršimonš produced what is generally regarded as his masterpiece. First built in 1865, the "Allegrettos" were the equal of every task entrusted to them and always had some reserves of power. They quickly took over all fast pasenger work throughout the RSR network and revolutionised the schedules in the process. Start-to-stop timings of 30 minutes for the Kropčahne-Bevice run were no problem, despite steadily increasing train weights. The "Allegrettos" outlived several later types and were the mainstay of lighter fast services well into the 1890s. The first built, "Allegretto" herself, was preserved in the Bevice Museum of Science and Technology on withdrawal in 1887.