I have duplicates of most if not all the attachments. I would me happy to share my duplicates with you. Maybe we could figure out how they work!!
The other style you see is a groove at the top for the thread. It works the same way. I am trying to sort out whether or not my badged treadle head was a New Home, as it looks similar to this. I love my treadles, but it's a lot easier to research Singers!