What about very carefully applying a little heat to it? If you can get the outer piece to expand more than the shaft, it might come off. I'd hold a match over the round disk and let it heat from the bottom of the flame, no warranty implied or otherwise! Or touch it with a small soldering iron. It's not plastic, is it?

1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.