BCP
I remember this discussion topic well, and I posted several responses. There have been several engines referenced as the possible origin of this tender tank, and none so far fit the major details of the current tank (in my opinion).
I have looked at many railroad pics (not all locos of every NG railroad), and have not found a viable candidate for the origin of the tank in question. I will be happy to "argue" any specific engines (and their tenders) as the origin of this tank. There should be a photographic proof of this specific tender somewhere in history, however, it may be after it's parent engine was scrapped or disconnected from her....
Casey