This is an unusual sewing machine as it feeds material different from all other domestic sewing machines. Commercial sewing machine use walking feet to feed material while sewing and this domestc is close to that very nice system. VF stands for Vertical Feed and this one advances the material, not with feed dogs, but with the needle and the presser foot. It is fun to watch this one sew and this is the best way to 'see' how it works.
Understanding how this method advances all of the material together at the same time so that all surfaces of the material remain in the exact same position during stitching. In quilting all layers of the quilt being put together remain where you place them since the needle, while in the material advances the material preparing for the next stitch. All layers stay where you want them.
This machine was manufactured near the turn of the century and was made to use in a treadle for the most part. This one sewed perfect stitches when I threaded it and turned the handwheel to make a stitch. The price of this very nice Davis VF2 is $237.50.