If it's like the other BelAir posted it has a drop in class 66 bobbin. I really want to see the underside. If it's gear driven then it's a 201 clone. It could just as easily be based more on a 66 with a 15 style stitch length selector though.
Try Singerco.com for either a 66 or 201 manual. They're free downloads. The HA-1 manual will have different instructions for adjusting your tensions.
Rodney