How can one tell if a Bernina spring-load foot (9, 24) is genuine or a knockoff?

Hello, I have two feet that came in a lot of sewing machine accessories that are identical to the Bernina website.  I have seen several posts where people say there are knockoffs out there that aren't as good and can even damage a machine.  There's a seller on ebay selling a bunch of knockoff #9 feet by making it look like in the auction they are the real thing with the title, and he's using the official Bernina photo.  Then says in the fine print photo is only an example so there's no way of knowing what his look like. I want to sell these, #9 darning foot, and #24 embroidery foot, but not until I know for sure what I have. I don't know if the knockoffs are identical in every way, markings and all.  I do know these are polished metal as they are so slick I had a hard time holding onto them for photos )  Thanks for any information!