While I am mostly ignorant of the historical aspects of the #1, I have often stopped at the park in Potlatch on trips from Eastern Ore. up to BC. It appears to me that the #1's tender has had some streamlining done by cutting and welding the corners of the front of the tender. My guess was that it had been a coal burner at some point in it's life and the tender might have seen this modification when the other updates for oil burning were done. Just a guess on my part. The engine is superheated, but it appears to have been originally a slide valve engine as the piston valve conversion is like that on the Nevada Northern Engines. The engine appears to have not been stripped to any extent like so many park engines. I have never climbed into the cab, but have stepped over the rope surrounding it to look more closely at various points from the ground. It would be a great 10 wheeler to see restored and would be a perfect size to pull a 3 or 4 car pass. train on a branchline.