Rare Salesman Sample Model

This is a very rare, possibly one-of model chassis of a car or truck. 19 in. long but very heavy for its size. All steel made. Has incredible detail and parts that function like the real thing. Said to have belonged to a museum in Europe. Too detailed and too heavy to be a childs toy but possibly made by a toy co. like Marklin? What other toy co. would have made something this extravagant? Maybe built by a skilled machinist but it dates back to the 20's or 30's and seems more like a salesman sample car.

   The motor is a very large clockwork mechanism that powers the rear axle. I believe this to be the most interesting part of the car/truck. Has working rear drum brakes which leads me to believe it is a salesman sample. How else can the brakes be activated if not manually? Also, the steering and leaf springs work. Just an amazing model! If you have any idea of make or have seen a similar model please send me a note.