the top row of the key board and P thus
QWERTZUIOP
1234567890
The number was put between Y's to show that it was a number, and the whole repeated as a check. The contination of a message whose time group was 2330 would begin FORTYWEEPYYWEEPY. We could then find the position where this message started by single wheel processes, and as we already know the window position of the start, we can calculate the Ringstellung.
On the 1st May 1937 a new indicating system was introduced. The first two
groups (four letters each) of the message were repeated at the end. This clearly
showed that these two groups formed the indicator. The repetition also showed
that no check could be expected within the first two groups themselves. This
was discouraging, as the essential weakness of the boxing method was that
the same thing was enciphered twice with the machine. With the new method
of indicating, whatever it is, the best one can hope is that either it will
enable us to 'set' the messages, or that from some information about the setting
of the messages obtained from elsewhere we may be able to deduce something
about the machine setting. However the first thing to be done was to find
out how the indicators worked, and it was necessary therefore to try and read
some messages with which the new system was being used. To do this one can
use the FORTYWEEPY messges, and apply one of the methods described at the
beginning of the last chapter. In this way the Poles found the keys for the
8th of May 1937, and as they found that the wheel order and the turnovers
were the same as for the end of April they rightly assumed that the wheel
order and Ringstellung had remained the same during the end of April and the
beginning of May. This made it easier for them to
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Back to Turing's Treatise on the Enigma. Chapter VII.