I would say check the clockwork mechanism with that of the M1 loco you have in the same lot ... I have a sneaky sneaky feeling it might be a hornby loco motor grafted into the Bing body Arne showed you on the other thread , the wheels just arent screaming Bing to me ( I have been wrong in the past ) and perhaps the Hornby motor has the key position a tad offset than the original Bing , hence the modified cut-out?
Normal bing loco and wheels