The Franz Krull Sk-class is a class of steam locomotive built by the Franz Krull metal works of Tallinn, Estonia between 1931-1940.

[1] The Sk were narrow-gauged and used oil shale as fuel, since it is the primary energy source in Estonia.

A total of 16 units were produced, of which none has survived.

These locomobiles were decorated by the red star and hammer and stickle figures.)

This article about transport in Estonia is a stub.