Originally Posted by Macybaby

that is a nice one! the first Improved Family machines are similar to the later 15, but they have a different hook assembly and take smaller bobbins. The early Singer Puzzle Boxes for the IF has a smaller bobbin holder and the class 15 bobbins don't fit. The later puzzle boxes have a wire bobbin holder. The attachments are the same between the IF and the later 15.

I have two IF machines, the earlier one has a different way to adjust foot pressure and the bobbin winder was on the belt guard. The later is like yours, where the foot pressure setting is on the head of the machine, and the bobbin winder is attached to the machine.

Did you get a manual for yours?