Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

That is just a old Marklin-type tray not attached to the engine at all.  There is a small leak on that end of the boiler and the tray catches the little bit of water that leaks out of the end cap, if that makes sense.

 I was referring to your cast base having an opening where mine does not. This might have been to fit a tray to run water through the pump if the engine is equipped with one ? most don't have their trays but I think that's what the open base was for.