Update

I’ve added links to files from the NSA’s Friedman collection in some of my essays. Specifically:

1). In State Department’s strip cipher – reuse of alphabet strips and key lists I added links to the State Department security survey 1941 and 1943.

2). In Japanese codebreakers of WWII I added the book The Japanese Version of the Black Chamber: (the Story of the Naval Secret Chamber) by Toshiyuki Yokoi

3). In US diplomatic codes A1, C1, Gray and Brown I added the report ‘Communications systems in use by the Department of State’ and the State Department security survey 1943.

4). In The American M-209 cipher machine i added the M-209 manual from 1944.

5). In The US Division Field Code I added the DFC No 4.

I’ve also added links to Mark J. Blair's M-209 Group and Top Level Telecommunications.