dhagest245,
Welcome to the QB forum.
Your button holler will not fit your Singer 66-1 machine. Your machine has what is called the "BACK CLAMP" feet, the button holler is designed for the later machines with the "SIDE CLAMP" or low shank set up.
I do not know if there ever was a back clamp button holler. Singer discontinued the back clamp design on the model 66s in the early 1920s. Many many Mdl 66s were converted to the side clamp / low shank presser bar so it can be done. As inexpensive as they are though, I'd just go get another 66 already with low shank feet.
Joe