You need that plate with the gear on it to make it work. That gear rotates and moves the whole buttonhole attachment and the fabric around to create the buttonhole.
Hard to say which machine it goes with. Each of my two Kenmores has a different style of buttonhole attachment.
I'd look on eBay and see if you can find one with that information.
Last edited by mlmack; 07-03-2013 at 10:11 PM.