[Kevin in NJ]

You must specify which part as the mechanical process for prep or final buff would be different depending on the part. The spark and throttle levers are just buffed shiny while other things were done to the dash or door handles.

During the A production (and later) they did not use the bright nickel plating process. They used a dull nickel process that was buffed out. This is what gives the dull grey color on the back of the bumpers and landau irons (for cabriolet).

There were some other processes for 'butler' finishes, but they still used a dull nickel tank. I do not know the processed to arrive at these other finishes.