Brian Martin,Freelance adviser
That welder is made by Miller and distributed thru MAC tools. I would say that is a heck of a deal. We have been using a few of those at the shop where I work for the past 10 years or so every day and they are GREAT tools. Every part is available new from Miller if you need anything, that is a killer welder from the experience I have when them. My personal one in the shop was well cared for (I'm a little anal about this stuff) and it was like new when I handed it off to another guy a few years ago and he is still using it on a regular basis.
Here's a Miller on ebay. It's at $360, that on on craigslist is a KILLER deal! Be ready though that tank may not be the guys who is selling the welder, they are often rented and not sold. So it could be owned by a welding supply company. I don't know what to look for on it, but if there is a company name on it like "AirGas" or something like that, it could be owned by that company.