There are 2 screws that the piston chamber is partially covering on your unit. The original units have a bellows, yours has been upgraded to the piston kit that was sold by Gilbert. I don't know if you can get to the screws without removing the piston chamber that attaches to the front of the smoke element box. The black wire comes up from the front truck rivet and you will have to get the smoke unit plate out of the way to have access to that rivet.
S.I.T.= Smoke in tender. The early post war Flyer engines had a separate smoking device in the tenders, that used an electric motor to force smoke thru a rubber hose that ran to the engine. If you look at the first picture you can see a brass tube that the hose connected to the stack in the engine.