That helper was made for (primarily) holding driveshafts ) out the door when installing new "U" joints. (Made from junk that was around)
I got my start with No 6's in the early seventies, finding one broken in a garage barrel near my house. Got it welded for something like ten bucks and it lasted for more than twenty-five years. When it broke again, Princess Auto offered me a LIFETIME warranty even with that vises' history. So that's how I ended up with the new one in the pic.
You know yours (and mine) is the later model, as the earlier one I had, had closed in mounting holes.
They will last a lifetime if properly cared for..............