New used machines: I have a blue Universal clone AND a black Universal clone both with busted throat plates right at the needle and the same break. Other than that they are remarkable machines. They were REALLY filthy.
Then I got a Universal that is suppose to have disks - none there. I have no idea what to look for. BUMMER... BUT it has the owners manual with a price of $359.00 and the original tags etc with the machine. It had pretty light use. I think they gave up when the bobbin area got full of lint. I sure wish I knew what the disks look like. Maybe the manual will show something.
I also picked up a Montgomery Ward with one disk - zz. It has a thing that looks like a zipper foot that sticks up when the button hole goes - at least it looks like it does - I should have shot a pic. I haven't cleaned on it yet. I got it cheap - I figured it had a nice cord if nothing else. I think it is a winner and will work fine. It came with 3 bobbin cases - one broken... and a hand full of attachments and bobbins.
I got two other machines but I don't remember what they are - didn't get the cases open - I had to mow.