Update

I made the following changes:

1). Added pics from Foreign Military Studies B-644 in The RAF Cypher 

2). Added the following paragraph in Polish Stencil codes and secret agent ‘’Knopf’’

The person who was responsible for this success at OKW/Chi was the mathematician Ernst Witt. According to TICOM report DF-176 ‘Answers written by professor doctor Wolfgang Franz to questions of ASA Europe’, p11

‘The most successful work along with that on the Am10 was that of professor Witt, who very skillfully solved a cipher of the Polish Government in Exile in London. This was a large complicated grille which was laid over a large number sheet. Several such grilles were constructed and messages were read currently. Photographic aids were used in the process.’

3). Added the following paragraph in Soviet naval codes and the Arctic convoys

The compromise of the routes of PQ17 and PQ18 from reading Soviet naval aviation codes is confirmed from another source. The Swedish codebreakers were able to decode German messages travelling through their telephone network, even if they were enciphered with the Siemens T-52 cipher teleprinter. Some of these reports mentioned the decoded Soviet messages dealing with the northern convoys. The Swedish codebreaker Sven Wasstrom, who examined these messages, became distraught at this drama.