 The Post Office team developed a Bombe attachment for a standard three-wheel Bombe containing high speed wheels and an electronic sensing unit.It was attached to the Bombe by a very thick cable and was dubbed the "Cobra" Bombe.Twelve were made at the Mawdsley engineering factory in Dursley, Gloucestershire, but turned out to be unreliable, so the other stream of development at the British Tabulating Machine Company at Letchworth was preferred.