When shopping for AHM BL-2 Locomotives be aware of some differences.The early models appeared around 1962 and are equipped with 5 pole vertical motors, metal drive gears with brass axles and current collection from both trucks.The wheel flanges are the deep "NEM" contour, also there is a long screw attached to the frame for removing the worm gear.The cover plates on the truck frames are secured by one self tapping screw and one screw with a nut. The couplers have metal hair springs for centering.The next ones from the early '70's switched to plastic framed 3 pole vertical motor and plastic drive gears with plastic axles.The boss for the worm screw is still present on the frame but no screw is provided. The wheels continued to have the deep flanges.Electrical pickup is from the front wheels only.The late '70's early '80's models went to a different coupler mounting design on the truck ends and plastic integral spring couplers.The cover plates on the truck frames are now secured with 2 self tapping screws and a change to the smaller flange "RP25" wheels. Note that on these the clearance notch on the ends of the body is deeper than the early models, and is tough to spot without measuring.The AHM BL2 was never offered with the later style RSO drive and died when AHM closed up shop.The roadnames offered were all correct for this locomotive and were C&O, Miss.Pacific,C&EI, Rock Island, BAR, FEC, Monon and Western Maryland. The only other railroad that ever had them was the Boston and Maine, and they were never offered in this roadname by AHM.