I think it’s a gyroscope of some kind. The interior section spins easily within the exterior frame. There is a heavy metal wheel within the steel torus section. If I jab at it with a pencil eraser I can get it up to significant speeds where it becomes very difficult to move or hold onto.
The lettering on the top frame reads “MK XII-3 GYRO”
Pic 1
[
URL=http://img130.imageshack.us/img130/6083/dcp3656fr6.jpg]Pic 2
Here is a good site with information.
Torpedo inertial guidance gyroscope?
here:
That is a course gyro for a torpedo. Goes in the nose (of the rocket) to keep it from wobbling, which adversely affects motion and acuracy at high speeds.
I think.
Damn!Damn!Damn!Damn!Damn!Damn!Damn!Damn!Damn!Damn!Damn!Damn!
Good guess, but that thing is huge. This object is about he size of the size of a softball.
With a link even. 
Sorry, very idiotic of me. I actually had a customer here and was typing as my they were telling me the car they wanted. Never buy a Mercedes off of a doper.
I found that site in googling, but (possibly incorrectly) imagined that this was a bit too sophisticated in construction for a circa 1930’s object, plus the fact that it’s all stainless steel seemed put it more into a post WWII time frame.
I see the sixth finger on your right hand gives you an edge when it comes to fast typing.
On hunch I used MK12 instead of MK XII and found this
