Thank you so much Cathy, for the in depth description. It will help, if I ever get around to sorting my attachments out.
I'm thinking that it was the universal hemmers that came with my model US New Home. I wasn't impressed with the hemmer I tried with it. It didn't seem to sit tight and had a tendency to wobble, even though tightened as best I could. I know years ago I really liked using the hemmer for a low shank machine I used it on. I just looked at some attachments that I have and I noticed there is some differences in the thickness of the metal so that where it slides into the bar would need to be wider.
Janey - Neat people never make the exciting discoveries I do.