I recently purchased an almost new supergrind 2000. It came with the attachment for Grinding chisels in the picture. I don't know if it belongs or if it something that was put in the box. I can't find it in any other pictures or online. Thanks for your help.
It looks like a crude vise jig for sharpening chisels & plan irons on bench stones / diamond plates (https://www.amazon.co.uk/Faithfull-FAIHG-TB-Honing-Guide/dp/B000X2935S).
That's an Eclipse style honing guide for plane irons and chisels, I have one hidden in my workroom.