On ebay: The two-speed crank (not hub) is original OEM equipment.Message 1 of 1 , Feb 22View SourceOn ebay:
The two-speed crank (not hub) is original OEM equipment. The crank's direct drive is high gear, and shifting the quadrant lever on the top tube works through a linkage back by the seat cluster to a rod running parallel with the seat tube which acts to trip out the pawls and lock the sun, lowering the gear by 25%.
Another example here:
from a museum, with period literature.