NavList:

I agree on the eddy current damping/brake, so it has to be post 1855.  The writing on one of the coils is English.  It would be nice to see a full rear view to see if the shaft enters.  I suspect not.  I thought I could see a basic armature looking down through the toroidal hole in the centre of the bottom view.  It would appear that the meter is a mechanical integrator giving revolutions made rather than a rate meter giving RPM.  Could a steamship calculate distance travelled from the turns of its propeller using such a device, or an electrical company measure the turns on a coil being manufactured? Alternatively, the large number inputs/outputs? on the front suggest laboratory equipment. DaveP