I have an old Hobart welder model RC-256. 79W serial number from 1979. I did a little online research and apparently these were really good really popular welders. I'm not exactly sure how it even got in my warehouse but it looks to be in excellent shape. I have a shop next store and I'll run it and test it before shipping to make sure everything is functioning. Does have the 4 prong plug but the mechanic is talking about putting on the three pronger which would be better for most people.
I hope I'm not abusing the For Sale section here and putting on a bunch of crap nobody wants. If that's the case just let me know and I will cease and desist.
Thanks, Bryan (253) 737-5268 Seattle, WA

Just remember that it is a 3 phase machine, not many people can use it that is the reason for the 4 prong plug

Not sure about this one but the welders we use on our building projects can be wired for most any combination from 208 3 phase up to 480 single phase. The photo of the tag does only say 3 phase so may not be the case here.