No argument about the boiler on both early and late 36" engines. All of them were built to burn propane using that awful blowtorch burner that focused a lot of heat on the tubesheet instead of where it belonged. I don't know for sure if Monroe just scaled up the boiler that was used on the 24" gauge locos or what. Chad O'Conner rebuilt several of them into oil burners, with success. Being from PA, and within a stones throw of Wyano I got to see several of the 15" and 24" Crowns when I was a youngster, and they all burned coal. The last of those that I personally saw in action was the concession that the William's ran at Idlewild Park in Ligoner, PA. It steamed well and the fire was usually only needed tended to at the main station. It lasted until the late 70's, early 80's when the concession was not renewed and replaced with those "tractors with flanged wheels" from Witchita.