There were two different types of mechanical lubricators used on the H-8/AG prototypes, Nathan on the fireman's side and Detroit on the engineer's side. Notice that we have included the 'bundle of snakes' on the Detroit lubricator above. There are terminal check valves included everywhere in the piping, this is something rarely modeled to this degree. If you are wondering what a 'TCV' is, that is what you see in the cylinder side pocket, they are used to control oiling to various components of the locomotive.