If I am not mistaken, I believe I own the same foot. If so, it is a button hole attachment. With the various adjustments on the device, you can establish the length of the button hole that it makes, the width of the zigzag stitch and the width of the hole in the middle. My mother or I have used it on any number of the older Singer machines, including the Featherweight. I agree with Palady, give it a try and play with the adjustments. I would be willing to bet that what you have is a "buttonholer."