What is this?
Its a crank handle holder. It holds the hand crank up and keeps it from just swinging around.
AKA Jock Strap.
In the day it held the crank starter handle up to the side, so it wouldn't catch on sage brush, rocks and sorts, in the middle of a two rut road. If you don't have a spring on the start handle to hold it out from engaging , I wouldn't recommend using it.