I found a used sewing machine that could be converted to a locking stitch for easy basting and removal of basting stitches. It also worked as a regular sewing machine as well. I cannot remember if it used cams for various stitches or not.. Judging from the overall look of the machine and the cabinet it was in I would think it was from the 1950-early 1970's. Do you know which make and model it might be from?