Photos: Code machines at Bletchley Park

One of the world's largest collections of Enigma cipher machines--famous for being used by the Nazis to protect communications during World War II--is to go on display at Bletchley Park in the U.K.

The Enigma electromechanical rotor machines were invented by a German engineer at the end of WWI and from the 1920s were used to encrypt and decrypt commercial, military, and government messages in many countries.

Enigma and other vintage cipher machines from across the world will be on display at Bletchley Park on the weekend of September 5-6, to coincide with the annual reunion of Allied codebreakers who had been based there and who cracked the Enigma code used by the German military, allowing allied commanders to predict and counter the movements of the Nazis.

More than 70 machines have been gathered from museums and private and government collections for the Enigma display at Bletchley--including devices from the U.K.'s Government Communications Headquarters, the National Cryptologic Museum in the U.S., and military museums elsewhere in Europe.

It will be the first time some of the machines have ever been seen in public in the U.K., such as the Swiss K model machine, which was used by the Swiss government to protect military and diplomatic messages.

The Swiss became concerned about the security of communications protected by the model K machine and from 1942 began designing a new cipher machine, called the New Machine (Nema). The Nema, seen here, remained in use in Switzerland from 1947 to 1963.