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This is a "top hat" stitch pattern cam/disc for vintage Singer sewing machines. The stitch pattern is a 3-step zig-zag stitch. The disc will fit the Singer sewing machine models in the 400, 500, and 600 series that take this style of discs. To be sure this is the right type for your machine, look carefully at the size, shape, and number of holes in the disc and compare them to the discs you have for your machine (some machines take a slightly different style of disc.) The original discs of this type were all black.
The holes in this disc may be a little to small to fit on your sewing machine. I measured them carefully for the design, but they sometimes come out a little smaller when printed. You can use something like a small round file or rolled up pieces of fine sandpaper to slightly enlarge the holes. Sand off just a little at a time, and check the fit on your sewing machine frequently. The disc should be snug enough to stay in place and not wobble, but not so tight you have trouble removing the disc.