24th Bonus

REF ID:A600359



U.S. Liaison Office


00/133/51                                                                                        25 May 1951 






Subject: French Modification of the M-209 Converter


Ref: (a) AFSA 041811Z May 1951 (409)


1. As instructed in the reference, I examined the modified M-209

converter in Paris on 21 and 22 May. We agree in the conclusion

that the modification is well engineered and that its use is

operationally feasible.


2. The modification consists of replacing the original fixed-slide

normal alphabet print and index wheels with demoutable print and

index wheels of approximately the same physical dimensions as the

originals, and that have radial slots in which metal type can be

set so as to provide any desired sequence on the wheels. For

convenient reference, Figure 1 describe the new type-wheel.


3. Cost of the modification is about $24 per machine. The movable

type print wheel is covered by a French patent concerning which

he indicated there whould be no difficulty if other nations

wanted to modify their own machines.


4. I think the proposed modification offer a great security and

I believe it is possible to consider the machine acceptable for

NATO use at third level, at least as an interim measure, subject

to establishment of satisfactory rules for use, such as bisection,

frequent change of alphabet and settings, good indicator system,

etc. Use of the machine by the French should increase the security

of their internal communications considerably.


5. The Colonel Veyron LaCroix authorized me to bring a decryption
exercice of two encrypted messages with their new machine. Your staff
can try to decipher them.




Commander, U.S. Navy