Wonderful Marklin rack-railway locomotive with windup motor. The Zahnrad locomotives from Marklin literally translate to “teeth” or “gear” wheel. The locomotives have these special gear wheels to navigate steep inclines. Marklin started making these special locomotives in the early 1900s. They required special track that have grooves for the gear wheel to lock into and slowly ratchet up the tracks. Later in the 1930s Marklin introduced an electric Zahnrad locomotive. Marklin produced such locomotives in O Gauge like this one and also larger ones in Gauge 1.