It was a double sided single sheet that folded up. I think I only used it a couple of times, many years ago. i really wouldn't want to use a regular zipper foot for an invisible zipper. Something that should be noted is that you install the zipper before seaming below the zipper. I also forgot that one side of the instructions is for polyester teeth and the other for metal teeth, although they look the same.
There is also a Coats & Clark invisible zipper foot.
Janey - Neat people never make the exciting discoveries I do.