Hot water, can you please explain why the drivers are stamped 605 on the 611?
Of course, and thank you for a logically stated question.
After reading this thread I m curious to know now.
Most of the large railroad heavy repair shops, generally called "Back Shops", developed more efficient systems for repairing/remanufacturing major components of a steam locomotive. Generally speaking, when a locomotive entered the shop, the tender was separated and moved to a completely seperate facility (called a 'Tank Shop'). The engine could/would then be lifted off of it's wheels, and placed on stands in order to access the various frame and boiler components, such as brake rigging, springs, driving boxes, pedestal jaws, appliances (air pumps, water pump, boiler checks, turbo generators, safety valves, gauges, cab fittings, exhaust stand & nozzle, boiler tubes and super heater units, and throttle components).
Major components were transported to specific areas within the shop for inspection and rebuilding as required/scheduled. Wheels and axle assemblies where inspected and new tires installed, maybe new crankpins installed, and any necessary machining performed on the axles. All side rods and main rods received new bearings, etc..
When the boiler work was fulling completed and all the appliances reinstalled, and the engine was ready to be re-wheeled, an appropriate set of completely rebuilt wheels and drivers were transported back to the main "Erecting Bay" in order for the engine to be lifted (by the big over-head cranes) and re-wheeled. If there were other locomotives of the exact same class in the Back Shop at the same time, it really didn't mater whether the exact same machinery components were returned to that same engine. The N&W Rwy. was one on the very best developers of highly efficient component rebuilding, with very quick turnaround, so that any locomotive could be completely rebuilt, in the shortest length of time.
Thus, since the N&W J Class 4-8-4s were all home designed and built by the N&W, all the major components, like driver assemblies, where all identical, it never really mattered which of these components were returned to their original host locomotive, if there happened to be more than one J Class in the East End Shop at the same time. Whichever major components were rebuilt first, they would be installed in the first J Class locomotive ready to be re-wheeled, and finished. As a side note, the N&W also had a separate numbering system for their various classes of tenders, which were all built/rebuilt in a separate facility there in Roanoke (still part of the East End Shops complex). Thus, the locomotive number never appeared on the tender.