The prototype is almost certainly one of the 650 ton variety. At a minimum, Cheyenne and Laramie were both home to this size tower. I'm not sure if there were examples of this capacity built for any other locations.
A google search will come up with lots of photos of both the prototypes and also HO models by IHC (in plastic) and Overland (in brass). Pics of another O scale model can be found on a separate thread here on the OGR forum. There is also a very nice UK exhibition layout called Laramie Engine Terminal which features another example of a scratchbuilt 650 tower.
Jim
