On Bachmann's Spectrum HO Russian Decapod there is a short right angle pipe fitting sticking out of a circular base on the left hand side of the race behind the steam dome. What is the function of this fitting on the prototype?
Bob See attached photo from page 61 of MR/Linn Wescott's Cyclopedia Vol. 1 - Steam Locomotives. The mystery fitting appears to be a valve handle sticking out of an opening or recess in a shallow dome directly above the air pump and just forward of the fire box.