A coded note from an antique clock

The NSA museum forwarded me a request. Can a reader crack this encrypted message that was hidden in a clock?

May I state something to start with? I’ll just do it: The daily newspaper Tagesspiegel published an article about me. I feel very honored.

Quelle/Source: Tagesspiegel

The article is free, but you have to register.

The Sessions Clock

But that’s not enough honor (and bragging): the NSA also contacted me recently. More specifically, it was Robert Simpson, staff member of the NSA Cryptology Museum, who thankfully forwarded me a request. The matter is exciting, but probably quite difficult.

The request came from Michael Balluch of Kansas. Mr. Balluch purchased an antique clock at an auction a few years ago. It was a U.S. brand Sessions device, which is now defunct. The following advertisement, which I found via Google, shows that Sessions was based in Connecticut.

Quelle/Source: Hifi Archiv

Here are a few pictures of the said clock that Mr. Balluch provided me. This is the front side:

Quelle:Source: Balluch

And here is the reverse side:

Quelle:Source: Balluch

On the following picture you can see the nameplate a bit closer – or what is left of it:

Quelle:Source: Balluch

The Sessions Clock Cryptogram

When Mr. Balluch disassembled the clock, he found a note inside:

Quelle/Source: Balluch

Apparently, this is an encrypted text. It is dated June 2, 1942. At the top left you can read “War Department” and “to be decoded”.

The interesting question is what this message means. The upper part consists of four-digit numbers, some of which are repeated. The two right digits each represent a number between 1 and 40. This looks to me strongly like a book cipher. Presumably, the two right digits stand for a book page, the two left digits for a letter. 3901 would be the 39th letter on page 1.

The bottom five lines mean nothing to me. The first four of them are almost identical and each contains numerous repetitions.

Unfortunately, I can’t make sense of the handwritten numbers on the right side either.

I don’t have to mention that this “Sessions Clock Cryptogram” is a tough nut to crack. If it really is a military message from the USA during World War II, there should be a good encryption method behind it. In any case, the US used good cryptography at that time.

If the upper part of the message was encrypted with a book cipher, then one will probably have to find the book used. The 60 characters of the message might not be enough for a frequency analysis.

A similar case

Incidentally, this case is similar to a story I presented on this blog in 2013. Unfortunately, since I was not writing for Scienceblogs at the time, that article is not archived. But there is a newspaper article about it that appeared a few years later.

At that time, watch collector Jens Treder from Soest discovered two coded messages in an old watchmaker’s book from a flea market. My readers were able to solve them. They were love letters. Such a solution would rather surprise me with the “Sessions Clock Cryptogram”.

Now I am curious what my readers say about the “Sessions Clock Cryptogram”. Like certainly Robert Simpson and Michael Balluch I would be pleased about many comments.

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