Just a little extra information about the construction of that vise.
In the intervening time between this and my previous post I've been cruising the internet looking at pictures of old bench vises and have found nothing quite like this old thing.
I thought the grip range would be up to something like 210 mm, but the real measure is 180 mm. Still quite fine for me.
My first impression was that the top cylindrical section was a protective housing around the screw which worked in threading cut into the wall of the casting. I tried to unscrew the bolts holding it to the rear of the casting and realized it was locked to and moving with the threaded rod. In fact, that cylinder on top is also solid, but bored out and threaded internally. It probably has a section that extends beyond the rear flange and fits into a bored socket at the rear of the housing. I didn't bother taking it all the way off, but snugged the bolts back down tight and unscrewed the vise far enough that I could give the threaded rod a good coating of graphite grease.
The design is so arranged that when opening the vise no threaded portion of the shaft appears until the vise has been opened to at least about 8 or 9 centimeters. The shaft that does show normally is a very close fit in the hole bored into the casting, no doubt preventing the ingress of work swarf and contributing to little wear and almost zero play in the action of the thread when turned.
In the intervening time between now and my previous post I've been cruising the internet looking at pictures of old bench vises and have still found nothing quite like this old thing.