Franz Krull Sk class

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

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. The last Sk, Sk-156, was scrapped in 1980 in Beloretsk, Russia, where it was actively used until scrapping.

List of Sk locomotives
Built in 1931:
 * Sk-151
 * Sk-152
 * Sk-153
 * Sk-154
 * Sk-155
 * Sk-156
 * Sk-157
 * Sk-158
 * Sk-159
 * Sk-150

Built in 1935:
 * Sk-160
 * Sk-161
 * Sk-162

Built in 1940:

(During the first Soviet occupation of Estonia, when the factory was renamed "Punane Krull" ("Red Krull"). These locomobiles were decorated by the red star and hammer and stickle figures.)
 * Sk-163
 * Sk-164
 * Sk-165