Hi David - as far as I am concerned there are essentially two variations of the Autavia 2446C GMT as follows:

The 1st execution has smaller sub registers, engraved backcase, smooth pushers, plain steel hands, white chrono hand and larger internal diameter bezel with fine teeth
The 2nd execution has larger sub registers, plain/polished backcase, fluted pushers and bezel with larger teeth.

The bezels are not interchangeable.
The combination of hands (hour, minute and chrono) on later examples vary depending on when it left the factory and /or service history. I do believe that the final example had the red accent hour and minute hands and red chrono hand.

In the example below please ignore the hour and minute hand on the later example. These are much later service hands which are thinner than the originals.

Hope that helps.
regards
Paul
www.heuerworld.com