Zygalski sheets

Zygalski's device comprised a set of 26 perforated sheets for each of the, initially, six possible sequences for inserting the three rotors into the Enigma machine's scrambler.

[2]Like Rejewski's "card-catalog" method, developed using his "cyclometer", the Zygalski-sheet procedure was independent of the number of plugboard plug connections in the Enigma machine.

[3] The Cipher Bureau's manual manufacture of the sheets, which for security reasons was done by the mathematician-cryptologists themselves,[4] using razor blades, was very time-consuming.

The British, at Bletchley Park, near London, England, undertook the production of two complete sets of perforated sheets.

On 28 December part of the second set was delivered to the Polish cryptologists,[7] who had by then escaped from German-overrun Poland to PC Bruno outside Paris, France.