On my beat up 2C I have, the ring with the grooves, had to be gently tapped counter clockwise and unscrewed. The whole ring rotates around and out. Make sure you remove the set screw on the side.. Pretty sure there is one there.
Hope that helps.
I used a long punch and a small ball peen hammer to gently persuade the split ring to start moving. It doesn't take much force. Be especially cautious when you are close to completely unthreading the split ring - if you are not careful it will fall out onto the floor. And if it breaks you are out of luck.
The problem that I had the most difficulty in overcoming was loosening up the large bolt that attaches the swivel base to the stationary jaw tower. It looks like a giant slotted head screw. Mine was stuck. I mean really stuck. I don't think that it had ever been loosened once it left the factory. Even after I bought a drag link socket and was using it on my impact gun it still took the maximum pressure from my air compressor to finally get it to break free. I am in the middle of restoring mine now. And it is looking pretty good. I can post up a few pictures if you are interested in seeing the color I chose for mine.
Proctor: instead of starting a thread on it's own you might post up your questions with pictures on the vise repair 101 thread and there are also plenty of answers already for these old Reed vise restorations on that thread so give it a look.
also post up pictures of your REED 2c here too cause we all like VISE PICS.
another way to remove that split nut I hear is to use your wrench for your hand grinder that might work. also a drag link socket is maybe the best tool to take the bottom bolt off your Reed or some of the guys make one if they don't have a drag link socket in their toolbox.