From "What is the idea with this?" of last week

It is a factory 1940 Chevrolet spinner steering wheel, and the small circle in the wheel is independent of the rest of the steering wheel, making it work like a "necker" knob... that is - you never have to lift your hand or adjust your grip once you have your hand wrapped around the small bar inside the small circle, you just make circular motions with your arm while maintaining your grip, and presto, you could keep your other hand on the shifter, or your girlfriend.
Thanks to Curt and Jim on the "What is it" forum of the Antique Automobile Club of America http://forums.aaca.org/ubbthreads.php/ubb/postlist/Board/58/page/1