Joe,
I have a 252; and a 457. They are ZigZag and have metal and plastic in them. Interestingly, when I purchased a manual for them, except for their numbers and a few words, the manuals for the 252 and 457 are the same. My 778 needs more loving care than I am able to give it. It is a Touch and Sew. I have the cams and some other parts.
I really like the 252 for a ZigZag.