[sanddrag]

I just bought a very similar machine, although ours is a late 1980's and has a different brand name plate stuck on it, and a bit of a different variable speed drive on the head. As indicated by the big letter "M", it has "Meehanite" castings, which I've read is preferred for Taiwan mills. The OEM may be "Gain Shin" in Taiwan. Aside from the head, the machine appears very similar to their GS15V model, which shows up under Enco "Turn-Pro" Part Numbers 307-3678, 890-9987 and 890-9988. Be aware though, the Enco web page is showing a picture of a machine with box ways, whereas my GS15V has dovetail ways. It could just be a generic picture on the Enco site. The machine is very similar to Precision Matthews and all the other Taiwan mills of the era, and of today. It's not a Bridgeport, but it's also not $15k+ new. I'll take a good condition Taiwan mill over a worn out Bridgeport no problem. Although I haven't milled anything on ours yet, I'm very happy with it so far, for what we paid. The base is rather banged up, but all the important parts are in good shape. The only think I wish it had was hand scraped ways, but beggers can't be choosers.

I'd take a dial test indicator and mag base over to the machine, and thoroughly check it out: Check spindle runout, quill play, perpendicularity of the table to the column, flattness of the table, etc. If you can, take a few decent flat screwdrivers with you to tighten up the gibs. If you can't just snug the axis locks slightly before jogging it. A worn out machine will be free moving in the middle of travel, and tight at the ends of travel, and that type of wear is not something that can be fixed with adjustment. Go over all the ways and sliding surfaces. They should be coated with oil, and there should be no rust present.

A knock in the head sounds concerning. Could be a broken gear tooth or something. You probably don't want to get into a head rebuild.

I don't know what the market in your area is like, but I wouldn't go more than absolute $2k tops for that mill, and hopefully that's with a 6" vise on it. You should also consider the cost and convenience (or lack thereof) of moving it to your location. It's about 2400 lbs. Ours came on a pallet, and cost me only $60 to move, since I was able to do it myself with a hydraulic drop deck trailer.

For reference, at machine tool auctions, I have seen:
Step-pulley 1980s Taiwan mills in good condition go for $800-$900
1980s variable speed head Bridgeports with working 2-axis DRO go for $1600-$2250
Year 2013 "Clark" brand Taiwan mill with DRO and variable speed head in like-new condition go for $4,000 with a 6" machine vise.
*To all prices, add 15% buyer's premium and 9% tax.

The equivalent of that mill new is about $6500-$7000 brand new, with DRO, all day long. Also, there's a bunch of different Jet brand mills in the price range available with free residential lift gate delivery from Southern Tool, so you definitely have to look at the total acquisition cost, including moving it.