This single-cylinder steam engine of English or German origin was manufactured towards the middle of the 19th c. Without any doubt, it is the Department's most interesting exhibit, as well as one of the Museum's most valuable assets. It was used at the saw-mill owned by families Vilesti and Vilhar in Prezid, Gorski kotar, all the way until 1939, when it was donated to the Museum of Arts and Crafts. In 1958, the said Museum ceded it over to the Technical Museum. The engine's power is 50 HP (36.75 kW), while its rpm is 56 (it is a slow-movement machine), using 8 bar saturated vapour pressure (being a medium-pressure engine). Steam is distributed through a shell-like distributor. After a single expansion, steam is released into the atmosphere (with no condensation). The engine is equipped with Watt's centrifugal regulator for automatic rpm regulation.

The engine is displayed together with a 1910 boiler (not of the same origin, though).

The engine is very interesting from the educational point of view also, because all of its elements have real "textbook" shapes, permitting easy observation of all its basic parts (cylinder, piston, fly-wheel, regulator, etc.). Using the installed electric motor, the engine's operation may be clearly demonstrated to the visitors.