Pre-war Configuration: this will include UP-3 and UP-4 locomotives with road numbers ranging from 9015 to 9054. Unlike the UP-1 and Up-2 locomotives, those in this group are all equipped with front-end throttles, they also utilized fabricated frames and steam cylinders. This configuration features a boiler-tube pilot, matched drivers, three (3) exposed sander lines and ‘early’ style rods with Alemite grease fittings. The cab has an extended back wall to allow for a new brakeman’s seat behind the fireman, a ‘greenhouse’ type extended engineer’s sliding side window and it retains the original sliding ventilators on the roof. Because this configuration existed during the railroad’s transition period, both ‘early’ and ‘modern’ style graphics are appropriate. A near as-built style 18C 18,000 gallon tender is included with this configuration.

Post-war Configuration: this configuration became the final evolution of the class, most all UP ‘types’ in service after WWII received the treatment shown immediately above, once again, UP-3 and UP-4 locomotives and road numbers 9015-9054 are included. Common major characteristics for the ‘postwar’ rebuilds were: retro-fitted cast steam cylinders, five (5) exposed sander lines, Boxpok style #3 main drivers, strap iron ‘ATC’ equipped pilot, late style trailing truck, late style main & side rods, E-2 radial buffer, relocated and widened cab, modified side cab windows, hatch type roof ventilators and modified air pumps. A modified 18C tender equipped with a stoker engine relocated from the locomotive, extended coal boards, an engineer’s grip box, re-railing iron hangers and ‘modern’ style graphics accompany this version.