I agree with the others - It is clearly multi purpose (imho) foot. The indents on the sides and ability to slide back and forth clearly make it a zipper foot. The U shaped bracket for the screw/clamp, my guess, has two holes in it for the "guide" to slide into and the clamp would apply pressure on it and hold it in place. Here is a site that has a pic of a similar one with the guide (the picture is about 2/3 of the way down the page). It appears to have come with a used White machine.
https://tanitisis.com/tag/sewing-machines/
and just the foot is here
https://tanitisis.files.wordpress.co...pg?w=300&h=248
Cool find! now all you need to do is find a guide that will fit it!!