A three-motor German Enigma machine is among the top lots of Bonhams' Fine Books and Manuscripts sale in London on April 13, with an estimate of £140,000-180,000 ($206,723-265,787).
The lot was made in Berlin in 1944 and is one of only a handful of surviving examples.
Bonhams comments: "It is unknown exactly how many enigma machines were made, but we know that few survived the war.
"Rather than have the machines fall into enemy hands, they were destroyed by the Germans upon retreat and documents pertaining to their manufacture were burned or in many cases simply lost.
"On top of this, Churchill ordered all Enigma machines to be destroyed at the end of the war, so few machines remain intact."
The world record for an Enigma machine stands at £133,250 ($208,137), set for a specimen that appears in the 2001 film Enigma (starring Kate Winslet).
A letter from Ada Lovelace (1815-1852) is likely to prove another highlight, with a valuation of $25,000-35,000 ($36,914-51,680).
Lovelace was the daughter of the great romantic poet Lord Byron. A talented mathematician , she became friends with Charles Babbage (creator of the Difference Engine – the world's first mechanical computer).
She is credited with creating the first algorithm designed specifically for a computer.
The letter is addressed to the journalist Albany Fonblanque and reads in part: "Have you forgotten your promise to come here? The weather seems now very tolerable (& sometimes really delightful). — Babbage is here. I hope you will come before he goes."