So with the odometer and the speedo drive sorted out, it was onto the movement and the case. This is the movement as it emerged from the case:
The movement appeared intact on inspection, indeed it was just caked in grease and the debris from the mangled drive wheel. It was a simple matter to strip it down, then we sorted the various assemblies into separate pots for cleaning with pegwood, solvents & the ubiquitous toothbrush. Look at the colour of the solvent:
This took several rinses, followed by polishing of the wheels & arbors. There wasn't any tooth damage to the wheels, and the various pivot holes in the plates are all in good condition.
Reassembled & lubricated the speedo now works nicely in the electric drill.The picture below shows it in position in the main frame, hooked up to the main drive & the odometer. We cleaned the odometer wheels (very gently) with a swab dipped in a mild water/detergent solution:
Next stop was the case, which required a trip to the shed to find the top yoke, since there was no strap for the speedo and no idea of what it should look like. A cardboard template and some of the inevitable sheet metal work soon remedied that problem, and the case was rubbed down and sprayed gloss black. The picture below shows the speedo in position in the top yoke, from underneath:
The dial and needle we left mostly as found - we don't want to polish all the patina away. I had the lamp holder still attached to the original wiring harness, so this was polished up using brass brushes in the Dremel, wired up and fitted back in place. some new M6 nuts finished the job - since the design of these instruments originated in France, all the fasteners are metric.