I'd have to go out there and pull them out of the hole they are nested in but I think somewhere between 3.5 - 4.5 for the two I have here (one is a 40's vintage and the other 80'sWhat size? Those are great. The 5" has the pipe jaws too. Love to see a pic when you start.
Another 6" at the office (40s vintage) that is stuck closed.
I don't know what they called them back when they were new but I'd say they mostly resemble the "Machinist" style (NO pipe jaws).
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Hi Ron, I have the same vise, and it is missing the collar as well as the pipe jaws. Could you provide some side views of the pipe jaws with a ruler in the pics so that I could use them as a reference for building my own? Thanks. Hey Maui, sure I can do that for you. I'll post them tomorrow...

I'd be happy to post pix when I get to them. Might even be this winter. aside from brick, electric and insulation I'm mostly done with the new shop
(PIX here starting on page 2). TULSA- Concrete and Framer contractor recommendations
If you want to get rid of one, let me know.
If I let one go I'll let you know