In 2002 Charles Babbage’s Difference Engine No. 2, designed between 1847 and 1849, but never previously built, was completed and fully operational at the Science Museum, London. Babbage's purpose in designing the machine was to produce mathematical tables more accurate than any available in his day. To this end he designed a machine that could not only compute the tables but could also print them out and prepare stereotype printing plates so that the tables could be printed without the insertion of errors by human typesetters.
Built from Babbage’s engineering drawings roughly 150 years after it was originally designed, the calculating section of the machine weighs 2.6 tons and consists of 4000 machined parts. The automatic printing and stereotyping apparatus weighs an equal amount, with about the same number of parts. The machine is operated by turning hand-cranks.
The calculating section of the machine was completed in November 1991. After the Science Museum successfully built the computing section Nathan Myhrvold funded the construction of the output section, which performs both printing and stereotyping of calculated results. He also commissioned the construction of a second complete Difference Engine #2 for himself, which has been on display at the Computer History Museum in Mountain View, California, since May 10, 2008.