Looking to see if anyone has a lead on this part. Definitely a cast item doesn't look weldable. Checked marketplace and ebay with no luck.
If you poke around in either the Vise Repair (more likely) or Show us Your Vise thread, it will talk about it. I learned to do mine that way.It's not broken, despite the rough appearance of the ends. It is meant to be in two pieces and is known as a split nut. .
It’s 100% positive that your part is not “broken”. The factory snapped it in half in order to install it there in the front, behind the nose. It is a patented method of adjusting lash in the main screw. There should be a set screw bearing against that split nut to keep it in place once you get it tuned up to your liking. Reed vises, especially the R series, are among the best vises ever built. I’m sure other regulars on this thread will agree.I got it for free. A local bicycle shop closed down years ago and the owner said if I could carry it out the basement I could have it.
Also didn't know it was such a sought after vise.