Yost has been making vises since the early 1900's, and the 33C has been around for a while.
Mine isn't old, I bought it new about 2 years ago. If yours was built 30, 50 or more years ago, it is possible they made slight changes over that time.

FMC1959,
Another question if I may.
On my Yost the bolts for the swivel nuts have a small weld between the head of the bolt and the bottom of the vise.
Does your vise have that or are the bolts "loose".
Best regards,
Scott

I am not 100% sure if I understand the question.
Looking at the vise from the top side, there are no welds of any kind on the swivel bolts or the vise body.
I think you mean underneath where the swivel nut connects to I assume a bolt? Unfortunately I can't help there. My vise is bolted to my bench and I cut & smoothed off the excess part of the 4 bolts holding the vise down. Taking it off the bench to see under the vise is not a simple option.
Sorry![]()

Alinc: i live an hour from a few of those types of ships that are sitting in the Bremerton naval base. i haven't been on one of their tours for years and not sure they still have them, but i should maybe check and take a tour again now that I've got a true respect and liking for old US steel. that Rock Island with it's pipe jaws isn't a common vise and it would work well on any of our benches. i found this Craftsman version (picture attached) of it that Rock Island most likely made that i couldn't get the owner to ship to me so i'm still looking for one. thanks for posting and sharing your adventure with us.
Vintage: i tend to agree with you about the many advantages of owning several vises. that's one reason i'm learning how to weld is to make trailer hitch type attachments so i can swap out a vise on my bench if i need or want to for a different job or look.
Balane: so since you only have one vise which is a very nice Parker vise do you think you'll ever upgrade to a different one and what might that be? i'm amazed with all the versa vises you've bought and restored that you haven't kept one for those odd angle jobs or do you have one sitting on a shelf?
ALL: so Alinc's Rock Island vise was on the 1946 USS Missouri. i thought Wilton had the government contracts during WWII. i got my Morgan 50 off the USS Independence that was built in 1956 (picture attached). so wonder when Morgan got the contract? Rock island sold their vise company to Birtman electric in 1957 if i remember correctly. so Allinc your picture helps put another piece in our puzzle and thanks for remembering to take a picture with all the stuff that must have been going on in that little room and on that tour.
FMC1959,
One other question in addition to the Swivel Lock Bolt weld question...
Mine has what appears to be a serial number. The first number is tough to read and my guess is either a zero, a six or a nine. This character is followed 8258.
Yours is a couple of years old. May I ask what the serial number is?
Best regards,
Scott
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Alinc: ALL: so Alinc's Rock Island vise was on the 1946 USS Missouri. i thought Wilton had the government contracts during WWII. i got my Morgan 50 off the USS Independence that was built in 1956 (picture attached). so wonder when Morgan got the contract? Rock island sold their vise company to Birtman electric in 1957 if i remember correctly. so Allinc your picture helps put another piece in our puzzle and thanks for remembering to take a picture with all the stuff that must have been going on in that little room and on that tour.

I checked on mine and it looks like the S/N is on the dynamic jaw support part of the static. (first pic, red outline)
The 3rd pic shows the S/N; I didn't take the pic upside down, that's the way it is. In case you can't make it out well on the pic, it is 06043.


Outlaw: Did i forget to say it might take me a few weeks to read 1500 pages?![]()
just don't let SWMBO catch you at it! 
FMC and Sbose, since those are cast in numbers, and the plate would have to be stamped out and installed each vise, (you can see the pop rivets holding to the pattern) I doubt they are serial no's; it would be too expensive to replace the plate each time for each casting.
Probably either a mold/pattern number, or possibly a date code or Lot code for a batch of castings.
CW, You asked about vises that you trip over earlier. Mine isn't on the floor but on my work bench. It is an Emmert vise that has been sitting there for over a year. It needs some brazing to fix a cracked piece and I just can't seem to get to it or don't want to ? The one jaw I media blasted has hardly any surface rust after a year, maybe it is the metal it is made of.
My guess is a lack of wood vises would be this forum caters mostly to mechanical type hobbies and not to the woodworking guys.
I can fair imagine XCMTB83 buying a full set for peanuts and posting a photo of his latest acquisition.![]()





I have a nice # 3 Wilton for sale???
I will just leave this right here...![]()
My first vise refurb
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My next...this is fun..
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Proud dad with his 'new' bouncing baby bullet; it looks just like him! ;-)








I have a nice # 3 Wilton for sale???
Scott--The big question is how many water skiers could the USS New Jersey pull???