1. Once the indicating system of Porpoise (the name given to the new key) was discovered, rapid progress was made. Examination of the message setting used revealed the normal peculiarities that one gets when the operator is allowed a free choice. Keyboard indicators (i.e. setting such as QWE taken straight across a row of the keyboard) and "pronounceables" (EVA, KAR, ANT etc.) were used to a certain extent - though fairly well kept down by security regulations. A more valuable aid (and one of which the security officers were probably unconscious) was the preference of the operators for individual letters. K, L and M, for example, being on the lower right hand corner of the keyboard
Q W E R T Z U I O
A S D F G H J K
P Y X C V B N M L
were always popular letters. Vowels on the whole were very unpopular though there was a curious difference here between different blocks of traffic. Although Mediterranean, Black Sea and Aegean traffic were all on the same key the groups seem to have different security officers. On the Mediterranean traffic "pronounceables" were very popular so that vowels in the middle were very frequent; the Black Sea and Aegean authorities seem to have thought of this possibility and to have forbidden the use of vowels in the middle at all so that in these groups vowels were extremely rare. It is hard to say which of the two types of traffic was more useful to us. Another peculiarity which we found of great value was that indicators with repeated letters e.g. LLQ, KJJ, CNC were practically never used; the one exception to this was Mediterranean pronounceables such as BOB, TOT, ADA, ANN.
2. These peculiarities were of the greatest help in finding the true message settings. The "throw-on" system enables one to say that the result of encyphering at the Grundstellung is to give one of a fairly limited set of possible results e.g. one might be able to say
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