if you are buying top clamp Rotary (not just top clamp) I beleive with the later ones there are four styles, three wide and one narrow.
The Narrow fits Free/New Home, the wide has two styles, one fit White/Domestic and one fits National and all the various branded names they made, including the Montgomery Wards machines.
There is a fourth - for Standard, but I'm not sure if that set ever came in boxes marked Rotary - it is also a wide gap foot. All the Standard sets I've got came in metal boxes marked "Standard", not the more generic "Rotary" boxes
For National and White, the needle hole is centered, but the distance between presser bar and needle bar in the White is a bit longer than National. The needle hole is offset on the Standard - so the three all all unique. White is the most common, Free the next, than National, with Standard being the least common.
They all have unique shirr plates, and if the set is not had parts swapped out, that is the easiest way to "guess" which machine they fit. White is allmost square, National is also square, but the top hook makes a S type shape. Free is long and narrow, Standard is also long and narrow, but they are different enough to easily tell apart, and one is a narrow gap and the ohter wide.
Metal boxes that say "vibrator" are the long shuttle versions of the "rotary" metal boxes. I don't know if vs sets ever came in cardboard boxes.
If you get older sets, metal box or the flip top black cardboard boxes, most often saying "Attachements" they are older sets and there are many more variations, I think I'm up to about 12 of them. Though some the feet are the same and it's the slide plates that are different.
hopefully you've found some of my posts with pictures.
Last edited by Macybaby; 03-23-2014 at 02:42 AM.