This is a ruffler. It happens to be an old Singer ruffler being used on an older Elna sewing machine, but it works wonderfully!
My local sewing/fabric store, Caldwells, is amazing. I walked into the store asking for a $10 presser foot to do gathers. The sales clerk went directly to a $40 presser foot contraption (that almost gave me a heart attack!), only to discover that it was the wrong connection for my machine. (Whew!)
Then she went looking in their used pieces, brought out a ruffler like this and told me how they work.--She also commented that she had the $10 type of presser foot I was asking about and it didn't really work!
It took a bit of searching for the clerk to find the right size ruffler for my machine, but she did. $5 later, I was the happy owner of a ruffler foot!
And look what it does--in one evening, too! This is intended to be a skirt for my oldest daughter. I need her to try it on before I do any more finishing to it.
The ruffler is a wonderful attachement. It creates evenly spaced mini pleats and sews them to another fabric all in one pass. No more basting stitches to pull!