The Mark II was started in 1945 and it too used relays. It was three times the size of the Mark I and could handle 100 ten digit numbers at ten times the speed of the Mark I. Still you can't help being amazed that they were still building electromechanical computers at this late stage!
The Mark III
The Mark III, also built at the Naval Surface Weapons Center at Dahlgren, Virginia was finished in 1951 and the Mark IV in 1952 and both used novel electronic components - such as magnetic core shift registers.
The Mark IV
Aiken's later career
In 1946 Aiken was allowed to return to full time work at Harvard. In 1947 he was made director of the new Computation Laboratory - a post he held until 1961. In that time he fostered a great deal of fundamental work in computer science - mathematical linguistics, automatic translation, switching theory and the use of core memory and drums were all pioneered at Harvard. He was the editor of the Annals of the Computation Laboratory and wrote a number of books on switching theory.
He retired from the Compuational Laboratory to, in his words, "make money". Could this have been another late change of mind concerning his career! He set up Howard Aiken Industries and sold his knowledge as a consultant. Strangely for a man trying to make money he never liked patents and trying to prove who had invented something.