In fact, pretty sure I can see even in this photo that back steam dome nearer the cab looks removeable in this photo Zoom in on it.
Copied from that other whistle steam topic
Again, the lesson of the day is:
#1 All MTH that I am aware of ever made to this date that had steaming whistle, have some form of completely separate smoke unit not connected to the main smoke unit and thus MUST be separately filled for steaming whistle function. In other words, not like a Lionel with single stack fill.
#2 the fill location will vary engine by engine, and sometimes it's a removeable dome or other feature, or you are forced to fill through the smoke port (example J-class).
Again, MTH does not make in O scale "dual" smoke units that share a common smoke well and wick. HO, yes, maybe, but not O scale.
