Folks, I have cams for a Singer 328-K, and for a Singer 403-A. As was mentioned previously, I got 8 or 10 of the flat cams with my machine in 1963. The Singer 403 had only one cam with it, but I've been looking around and found most of the (I think) 21 made for the 403, the Touch & Sews, 600 and 700 series. The Touch and Sew top hat cams will fit the 403, but the white flexi-stitch won't work (so my son says--he worked on SMs for 14 years. I saw an auction listing on e-bay the other night for a lot of "50" top hat cams, listed for something like $69 or so. Then, there are other listings that have the Top Hat cams priced at $5 to $10 each. I have most of the ones for the 403, but not all! That's okay, I really don't need any more! I'm not familiar with a lot of the machines that use the various cams -- so I'm no help there!
Jeanette