With out see one, I would guess its the dryer mounted to it or some sort of filter, or a reserve tank, a place where compressed gas is "stored" till needed. I would be carefull of buying one like that, the ends where hoses hook to most likely have a odd ball connection and your aftermarket hoses won't work. Don't the A/C venders, Vintage Air, Hotrod Air, etc... have universal condensers? Thats where I would look, or head to the salvage yard and look around.
Joe
