The $3200 price that Wookie mentioned was for another one I had that was new and it sold right away.
Im a little confused here, I assume you have more than one, are you a dealer in them.
The one you sold for $3200 bought it new and only used for aviator grade 02 is therefore a commecial product registered to yourself.
Now another one you have for sale for $1000 I'm assuming this is not new therefore the question of where it came from and who the original owner was potentially becomes an issue..
The problem your customer may face is if these compressors are ex Government US or otherwise they were built for a military contract and as far as Europe is concerned they would not be supported if they end up in the public arena.
Now its not your fault or the fault of these surplus suppliers at auction houses. You bid, you win its yours. The issue is the liability for the product if it was originally supplied under a military contract and this is not the same as a similar or even the same product sold into a commercial application.
So customer rings up asks for spare parts, then finds out its an ex uncle Sam piece of scrap under a contract build and cant get spare parts because its an ex miitary product unless he buys under the NSN supply contract terms with say minimum 500 parts in a box or the product if he pretends its for a military contract.
The supplier by suppying spare parts then has liability shoved on him with the encumbent problem if his customer burns the house down with himself in it and the widow Jones starts a no win no fee claim.
You see where this is going.
Your new compressor used for Aviation oxygen will be registered to yourself and so you or anyone else would have no problem getting commercial spares for a commercial contract build including any new owner when you sell it.
By contrast these ex military surplus compressors more and more are being viewed by the product liabilty lawers as a potential problem hence your customer may be dissapointed by not getting parts for a pump he cannot verify.
And the supplier of the spares is also not happy if he has to load the product liabiliy premium risk to help some say an Ebay player out of the blue to sell junk ex army scrap into the recreational scuba arena.
Hence why second hand dealers of ex military compressors and ex military surplus dealers flogging off goverment surplus scrap to divers on this and other forums may find themselves questioned by it's members and potential divers as buyers warned.