I need to get out my ruler and put my presser foot down and get to measuring. I would just about bet that it's a low shank.
I found a ton of darning feet on Ebay all stating they are NIB from 15.00 to 50.00. I think that big 50.00 one is for the 6000 or 6600, whichever ones you were talking about earlier.
This is great. Lots of links to look at.
That is why I love this board. I can post a question and be honest that I know NOTHING and look at all this information!!
I bookmarked this thread so I can keep track of that diagram...it's a bit confusing, but I get it enough not to be afraid of it.