You know, you are right. When my husband first asked me what that thing was, I told him it was a buttonholer. Then I looked through the 191 manual and saw the pictures of the automatic zigzagger, and thought maybe it was that instead. Now I finally got it out of the box, checked the numbers on the back, and it is indeed a buttonholer. The zigzagger (shown on the following link) looks very similar and probably works in a similar fashion, at least as it zigzags down each side of the hole. And they both use cams.
http://www.ismacs.net/singer_sewing_...tachments.html
Originally Posted by harris4435
Looks to me like the attachment is a button holer. I am not sure about the case either.