Despite the tarpaulin, this trailer can be identified without doubt as a Wiegenfahrzeug - cradle vehicle - K 3 by which the cradle of the 24 cm Kanone 3 was transported. As towing vehicle, a s. Zgkw. 18 t (Sd. Kfz. 9) was usually used.
The Wiegenfahrzeug K 3 without the tarpaulin. Observe the mounting for spare wheels. (Image from Bildermappe eingeführte Waffen und Geräte)