Difference Engine
The Difference Engine is a mechanical calculator first purposed and developed by Charles Babbage in 1822 that was capable of computing several sets of numbers and making a hard copies of the results. Unfortunately, because of funding he was never able to complete a full-scale functional version of this machine. However, in June of 1991 the London Science Museum completed the Difference Engine No 2 for the bicentennial year of Babbage's birth and later completed the printing mechanism in 2000. Below is a video from Wired Magazine that gives a good overview of the Difference Engine No. 2 shown at the Computer History Museum.
Also see: Analytical Engine, Computer History