I picked up this
Wilton Flip-Grip at the flea market this morning.
These are often identified in the wild or elsewhere on the interwebz (and even by some right here on this thread) by the casting number on the housing (121079), but they were Model No. 594. The excerpt is from Catalog No. 123 (1971), which is when they were introduced. I am not sure if they were ever made bearing a patent number, and if a patent was ever granted, I have never seen the number published on DATAMP, vintagemachinery.org, or anywhere else.
They're not rare, but they're not exactly common, either. I know that
@Mark in Indiana, among others, have or have had them, and provided good info here, and
@KMScott has posted a drawing for a pair of insertable jaws, which are often missing. I also have seen them with a red finish and
@bluebolt posted a NOS example of a red one with both sets of jaws, linked
here. The jaws on these looks shop made, too long, and loose, and I will be removing them. Not a heavy-duty vise, but fairly solid and kinda nifty for home use. Little to no slop in the screw and the swivel base and the tilting action work fine, once I loosened it up.
(Funny aside on olfactory differences and the penetrating oil debate. The tilting mechanism was stuck solid. I asked the seller if I could tap it with a rubber mallet he had on the same table, he produced some PB Blaster, which helped on the spot with a few taps. An hour or so later, as soon as I walked it down the basement, through the outside Bilco doors entrance mind you, Mrs. Lugz piped up from upstairs about the smell! She can't smell Kroil or WD40 if it's under her nose, but just a skosh of PB Blaster and she's suddenly a bloodhound through floors with the "You're not using that other stuff again are you?!" comments.

)