I love my Singer buttonholer in the rose colored "space age" box, and I have all the metal cams for that one. BUT, it does not include a round "eyelet" cam, the closest it comes is with a 5/16" not-quite-round cam.
I gave my DMIL a 500 series machine and bought the newer style buttonholer for her years ago. That version did have a round eyelet cam. After DMIL died, we did not find the buttonholer, so I thought it was long gone, but today while I was over helping DD with the costume, she was digging through some drawers in DMIL's sewing table and FOUND THE BUTTONHOLER!. So now I have both the older metal cam one, and the newer version which will let me make better eyelets in DGD's velveteen Highland dance vests.
And DD will keep the second metal-cam one I bought on eBay.
:-)
Beverly