This came to me via a roundabout route. The main component appears to be an electric motor - or, with a small impeller on the front, a generator - and it was claimed to have dropped off an aircraft and picked up at Dunkirk. It was also claimed to be part of an aerial torpedo. I have severe doubts about both claims. Neither is the cable necessarily original.
But why does it have the angled splines around both main sections (rather like those of the German rifle projector / Kampfpistole grenade etc). there are no marks save for an enigmatic figur 20 in a circle stamped on it, but neither Waffenampt nor AD marks at all.
Any suggestions most welcome.