Source: Computer History Museum, date indeterminate
In 1985 the Science Museum in London set out to construct a working Difference Engine No. 2 built faithfully to Babbage’s original designs dating from 1847-9.
The project took seventeen years to complete. The calculating section was finished in 1991 in time for the bicentenary of Babbage’s birth.
Related Reading: IEEExplore, Oct-Dec 2000
The engine performed its first automatic error free calculation on 29 November 1991, twenty-seven days before the 200th anniversary of Babbage’s birth, which had been the original target