I made a study of them, and there are measurements you can take to narrow down what they fit. However if you have set with the underbraider, that part was unique for many machines, so unless it was swapped out it can be used to determine what they will fit.
I think I have over 50 sets that are unique. Probably for 10-15 different manufacturers, and then several variations for some as they changed over the years.
It's funner trying to figure out the sets that are pre-Greist!