This group of what I think are chaser grinding holders measures about 12" on each side, to give an idea of size. I call them chaser grinding holders because of the text on small one that's front and center. As you can see many have micrometer screws for precise adjustment. Were these made for use on a particular brand of grinder, for any tool grinder, or...? It is very unlikely that I'll do any chaser re-grinding since I don't do "volume" threading, but I'd really like to know a lot more about these. Maybe if I cleaned the crud off of them, a brand name or something would show up?