Ebikessf.com repaired the Schlumpf drive for me. Thanks Ilia! It suffered some shipping damage, one of the ears for mounting the chainring was bent, but it is much better now.
The above drive is a licensed variant of the Schlumpf drive that takes standard chainrings and crank arms. I obtained this one from Accountant.
This is a "speed drive" model that shifts between 1:1 and 1.6:1 by pushing the button in the center of the hub left or right with your heel. When in 1.6:1 the chainring turns 60% faster than the crank, effectively making the chainring equivalent to one having 1.6 times as many teeth.
This is important since the Cromotor is so wide it doesn't leave room for a wide freewheel. Usually only a single speed freewheel is used, and the smallest units have 16 teeth. So the front chainring needs to have a lot of teeth to pedal along with the motor at speed. This gives two gear ratios, one for pedaling without motor at low speed, and another for pedaling along with the motor at cruise speed.