I agree too, but would love to see the darning foot in action.
I have one in a box of fascinating feet, some marked "Swiss Made", and 2 of the seam guides.....some of the feet are totally unknown to me. And have an old green metal sewing machine that used to have cams....Vigorelli, or some such name
Also have a Greist buttonholer for use on a straight needle machine, and a Greist ruffler. I am not familiar with that brand at all, but they are almost identical to my Singer tools of the same vintage. I wish I had a manual to identify all my feet.