Sonderkraftfahrzeug (abbreviated Sd.Kfz., German for "special purpose vehicle") was the ordnance inventory designation used by Nazi Germany before and during World War II for military vehicles; for example Sd.Kfz. 101 for the Panzer I, and Sd.Kfz. 251 for the armored personnel carrier made by Hanomag.

The Reichswehr and its successor, the Wehrmacht began systematically allocating numbers to its vehicles from around 1930, including horse-drawn vehicles, cars and trucks, combat vehicles, and trailers. Sd.Kfz. numbers were assigned to armored, tracked, and half-tracked vehicles. Cars and trucks were allocated Kfz. numbers and trailers were designated with Anh. (Anhänger) and Sd.Anh. numbers.

Allocation of the numbered series was as follows:

Some combat vehicles, often based on existing vehicles in the Sd.Kfz. series and produced in relatively small numbers, weren't allocated a number and were only described with a name.

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