Found in a box of misc items including a number of threading-related tools
wire spoke bender/straightener?
Tubing bender?
Looks like part of a valve stem grinder.
Valve reface cutter, its missing a handle thar holds the valve stem to turn and cut
the part that sets at 4/5% is the carbide cuter
Uncle Jack is right. It was used on the two piece valves which had the cast iron head. The cutter is plain tool steel. It came with a handle that was attached to the valve with a set screw. As you cranked the valve the thumb screw adjustment on the left forced the valve against the cutter. Does not work on the modern valves as the cutter is too soft.
Yep, A valve face cutter. Mine had a little chain attached to the crank and tool that kept things together but made it hard to use!
Thanks, everyone. Mystery solved.