I have a Singer Weatherweight 221 made somewhere in the early 40's. It has been used hard but is still in great shape as it was well taken care of. I have the original case, instruction book, many of the special feet, 8 original bobbins and original cord. I have purchased a 1/4 inch foot and a walking foot. I don't have any idea what I should get for it and I don't want to cheat myself or the person buying it. Any suggestions?