This is an original equipment aluminum thermostat housing. It is GM part # 3877660 that fits  67 - 69 Camaros, 66 - 68 Chevy IIs, 69 - 73 Novas, 66 - 73 Chevelles, Corvettes and many full size cars. It has been media blasted so you can see what you are really getting. There is some electrolysis scaring and one tiny hole about where the radiator hose clamp would be secured. The part numbers were not blasted to preserve their condition and you can see the carb return spring "ear" is in excellent condition. These are getting hard to find in this nice of condition.