I am not sure about the older machines but my Pfaff has like a 9 mm throat plate/space - where my Brother, Kenmore and Morse machines are 7 mm. I ended up with an extra "snap-on" shank and have found that it fits and I can use it on all but the Pfaff, which allows me to use just about all of the other feet (except Pfaff) on any of the other machines. In fact I got one of those packs of 32 generic feet from Amazon. I have found that my Pfaff has heavier feet and hard to match up with anything else, and she is fussy. Just my experience. I did find I needed to adjust the spring tension on top a little on the old Kenmore and the old Morse as to pressure put right on the sewing. The main thing is when you are trying to use a foot you are not sure of that you turn the hand wheel by hand slowly and gently test that it will clear okay in the throat plate for sewing. That way at the slightest resistance, you can stop!! :-)
Marysewfun