This is the other one - the one that makes tiny little letters suitable for cuffs or collars or even a dainty little hanky.
These are pretty cheap on eBay - about $20 - and they work on all slant shank Singers. Keep in mind though, that you need a zigzag machine to make the satin stitch (so the 301 and 404 won't work.) You also need a special feed cover plate even though the Slant-O-Matics have an elevated throat plate system to bypass the feed dogs. Using the elevated throat plate just doesn't work for this, I tried it.
|Simanco part #161825|
If you've ever used a Singer automatic buttonholer, then this will be somewhat familiar. It attaches to the machine the same way, and you open it and insert cams in a similar way as well.