Thanks Grant, I had read it recently, BUT hadn't read the comments at the bottom. From now on, I'll be inclined to read them too! From what I read there, the Singer 66-1 is the only one with the back clamp attachments. Then with the 66-2 and on, the attachments were on from the side. I'm guessing that the rest of the Singers were all short shank and side clamping attachments until the slant needle machines came to have the slant attachments. It makes a lot of sense having the attachments fit a lot of different machines. I do have some Singer short shank attachments that are longer than others, but they all seem to work on my machines.