Steve, the other one does not fit. The opening for the needle screw is way too narrow. Maybe Singer went to a narrow screw on later machines. However that one is has an arm that is just a bit shorter, but maybe that would not matter. Though on the full upwards stroke, the arm is just barely over the screw.
I cleaned them up enough to see the markings - the smaller one (the one that fits) has a round stamp on the back. The other markings are the same between the two.
