Hey NICK , UH.....probably / maybe ? Worthwhile that is.
I'd suspect it is a No.574 , it has the base swivel? and no no pipe jaws . The ROCK Island brand hasn't seemed to have been MORPHED by a Counterfeit producer or similar.
It could be a ,uh ...... "Factory 2nd" from the now OLD DAYS ?
Many manufacturers did this with production line FLAWS or even the rare "Warranty Returns" .
Sold as legitimate but with ZERO Warranties of any kind.
Often all other specific indicators were also removed , like the MODEL NUMBERS !?!
These vises generally had indicators in the base and mobile jaw.
The pic also shows a couple things. There are 4 tiny "PECKS" in the back of the base. Looks like where the - "later model tag" would have been held in place ,with 2 or 4? hammer rivets.?
The - Birtman Electric Company - tag would have been there unless it was a "2nd" (probably) .
They were the actual? firm & manufacturer from like 1930 to 1957-ish ?? ?
A point of caution .? I find rather incredibly these things were not infrequently BROKEN !!!!!!!!?
Often the front jaw breaks off where it attaches / meets? the driven sliding beam.?
The swivel locking handle has been replaced with a now bent bolt , not uncommon of course,but......
Depending on manufacturer and model of course , there is most often a castellated or TOOTHED plate or jaw that locates the swivel more firmly in place without having to TIGHTEN that clamp to the point BENDING the handle .?
So caveat emptor ! :^)
It could be a good acquisition at that price. But DO study just what you are looking at.? Hopefully it is a good find !
I have several vintage Wiltons , but I believe my favorite is a peculiar "Backwards Vise" . Ironically and almost dreadfully it was indeed made in POLAND.? An - FPU Vise - sometimes called a BISON.? I inherited it from my father-in- law?over 20 years ago. The FRONT JAW is fixed. The Rear Jaw opens with comparatively very wide WAYS to support the loads.
Marty