Colossus computer
After the war the British codebreakers found out that the code machine was the Lorenz SZ42.  All the secret Colossus computers were taken to pieces, so that no one would find out about them.  The designs were destroyed.  For thirty years no one knew who made them.  Between the early 1990s and 2007, a working copy of a Colossus computer was built.  This can be seen at The National Museum of Computing at Bletchley Park in England.