In the Science Museum (ScM) in London exists an artefact named “Babbage's Analytical Engine, 1834-1871. (Trial model)”, of which pictures are online: http://collection.sciencemuseum.org.uk/objects/co62245. A very similar machine is shown in the Arithmeum in Bonn, Germany. The IBM archives also have a small photo of such a machine; both evidently replicas.
Astonishingly, the machines on exhibition and the photos present the back side with the cam drives, and not the front side with the calculation mechanics. Obviously this object has never been studied: No publication or other written information has been found, although it is apparently the first ever built processing unit for a programmable automatic computer.
So I took a deeper look on the replica in the Arithmeum in Bonn (kindly allowing me to inspect the replica freely) and wrote a short preliminiary report which refers to a second document, a collection of pictures (4MB) taken there.
Many thanks go to Tim Robinson and Doron Swade for information and support.