David,
The wiper looks a lot like the lucas wipers that used to be fitted to the top of the windscreens on Landrovers and many other vehicles during the 40's & 50'.and were still used on commercial vehicles in the 1960's.
Brian
8227
The Claes car now sports a Lucas / Land Rover style motor for its 3rd wiper:
However, experts (the ones I've consulted, anyway) seem to agree that no racing driver would have wanted/agreed to have a lump of motor in this position - bad for visibility and very dangerous in an accident.
I have sourced a marine item for my 4th Series, from Italy - since I found the old wiper mounting it seemed rude not to reinstate the thing... The new, hand-operated, stainless wiper assembly fits the old mounting perfectly and will I think look the part.