Hello: I have enjoyed reading about your desire to learn what this big foot is and I have a modern version of that foot and I agree with one of your other readers that it is called a Walking Foot. It is used to ease thick fabric through the sewing process and is also used by quilters to feed the thick layers of quilt through evenly. I also have a ruffler foot and it does not look like that, it is definitely a "Walking Foot", they are expensive, a modern foot like that costs around $300.00. Happy sewing!!!