Also - the above are all SINGER sets, Greist made aftermarket sets too, but not for the back clamp. Greist didn't have the "multi-hemmer" so all those sets have separate hemmer feet like the very early Singer sets (pre -Wheeler Wilson).
Most of the older Greist sets are for top clamp machines, some of those for side clamp use a bed mount hemmer - and I think those would line up for your 66 too. It's the set on the left. However the other attachments are side mount.
The set on the right is also side mount, and is very similar to later made sets, and I think they are still making sets that mount this way.
If you have more questions, please ask. I need to go make coffee cake right now.
