They are Swedish vices made by a company called SEVO, Spencer Franklin are just the agents.
Beyond that I can tell you very little more except to agree that they are very versatile and will grip very triangular parts as well as other odd shapes. I was lucky enough to acquire one some months ago, having seen another in a friend's workshop. Mine was a trifle sad and needed TLC but it came up a treat and is used often
I was impressed by the quality when I had it stripped out, most of the work needed was only to polish off rusty marks, oil and rebuild it with a light touch from Scotchbrite where it was needed. A new paint job completed it
Regards
Brian