I saw this ciao a few months ago on FB marketplace. I would have gone for it but it was simply too far. Since then I got a modern ciao mix, the tank was awful....not so much because of rust, but the fact that there was like 2 inches of sediment in the bottom. From the top, the tank looked really clean. But I used a USB endoscope, and once I turned the corner past the filler neck I saw the mess...I took pictures.
Even after a ton of rinsing with a pressure washer, I still had all this in there. So theres really no way to know your tank is truly clean unless you look! The water can run clear but you may still have junk in there.