I have been using a US Divers Cyclone compressor since 1968. It is a Luchard H6 which is slightly bigger (3.5 cu ft / minute at 2800 psi 3 hp electric and 5 hp gas) than the one on ebay. Judging by the weight it is probably all cast iron as is mine. They came with pretty minimal filtration, just a carbon packed tower. I have up graded it with condensators and a seive tower and aluminum frame. Parts are not available for them.
If it has seen little use it might be a decent buy at $400 but not anymore than that and just run it until it is worn out or breaks. They are pretty tuff machines.