The McEwen tank is part original, part restoration, part modern, and entirely relocated. There are unsubstantiated reports that it was one of the original 1890's main line tanks that was later traded to the Oregon Lumber Co. It was last used by OLC for a domestic water supply a Bates. When brought to McEwen it was complete except for the spout, but the tank itself was deteriorated to the point that it was no longer usable. OLC had poured about a foot of concrete in the bottom to try and plug the leaks. In 1977 we acquired a steel tank but lacked the means to to place it inside the wooden one, so the wooden one was dismantled. (We still have the bands; the wood was used for other projects.) The house is still original, but most of the trestle has been replaced in the 1990's and 2000's.
So, I guess it depends on your definition of "original" as to whether it meets Doug's criteria.