They have been a popular woodworkers vice here for a number of years particularly for those who also do a bit of carving or make more organically shaped furniture. Gets the work and the grain orientation where you want it so the chisel, spoke shave, etc can be used without too many contortions.
Probably not been seen by the UK members in a pattern shop as they are an American item. Bit like Pony clamps which were not seen here until 30 or so years ago as everyone just used sash clamps.
Axminster sold them for a number of years as well as some of the other specialist woodworking tool suppliers.
Spot the vice in this US pattern shop making patterns for full size locos, goor range of flywheel castings too.