I just had a thought. Yes ... it hurt.
The round flat disk on top of the machine in the drawing "could be" just a cover to keep lint and dirt out of the machine.
To use the cams, it "might" be that you'd have to remove it.
If that is the case, then some of these cams I've seen on eBay and here just might be what I'm looking for.
Well, I just ordered the manual from Relics. We'll see when it gets here.
Joe