(not mine)
You don't see these very often. The $1500 asking price seems to correspond with that fact.
https://www.ebay.com/itm/1973-Yamaha-RD350-NOS-Gas-Tank-Petrol-/184008804755
1973 Yamaha RD350 NOS Gas Tank Petrol
New Tank - Never mounted to a bike. There is a tiny flaw in the clearcoat (1st picture) that was there when I bought it 20 years ago. Otherwise like new condition. It actually came to me in the original box which unfortunately I no longer have.