Bid to $180,000 (£134,330), it was a Wetterkurzschlüssel or ‘Weather short Signal Book’ of a type used on U-Boats.
Published in Berlin in 1942, it runs to just 26 pages that provide basic operating instructions and pages of codes in numbers and letters used to send weather reports from various parts of the Atlantic.
This Naumberg 3rd edition lacked the folding charts of the Atlantic normally slipped in at the end, as well as the small booklet inside the front cover, and the red cloth covers were slightly warped by damp.
It is nevertheless an extremely rare survivor and was lotted with an earlier, 1937, second Berlin edition of the Wetterschlüssel, one probably used at the Wilhelmshaven naval HQ for the decoding of reports from weather stations.
All Enigma codebooks from the Second World War are rare, and those used on submarines are the rarest of all – firstly because they were made of paper that dissolved in water, but also because submarine commanders had strict instructions to destroy both the Enigma machines and their codebooks if they were about to be captured.
Some 700 U-boats were sunk during the war, and of the remaining 300, many were scuttled by the German Navy when the war ended in 1945, again without giving up their secrets.
The capture of early editions of this codebook in 1941-42, along with the seizure of Enigma machines – from a German weather ship off Iceland and a U-Boat forced to the surface before it could jettison its secret equipment and codes – played an important part in the breaking of the German codes at Bletchley Park. It also forced the issue of this revised edition of the codebook.