Langer correctly assumed that the Germans would make further modifications to the Enigma machine, and he provided Rejewski only with a commercial machine, wanting his cryptologists to understand the machine from a purely mathematical point of view.
Langer correctly assumed that the Germans would make further modifications to the Enigma machine, and he only provided Rejewski with a legally purchased commercial Enigma machine. His reasoning was that he wanted his cryptologists to understand the machine's internal wiring from a purely mathematical point of view.