As pictured above, these gorgeous looking and fine running models were sold in both coal and oil versions. They are extremely rare and hardly ever show up on eBay, so I'm assuming the production numbers must've been quite low (even by brass standards). Internally, these are very similar to Samhongsa's SP Cab-Forwards of the 80's and 90's -
The two-part chassis is all metal and fairly minimalistic (with most of the actual heft being provided by the shell). Like the prototype, the forward engine is articulated (IE, free to pivot), whereas the rear engine is fixed in place to the shell. A fixed (IE, non-operational) coupler is mounted to the pilot. There is no coupler on the tender (although a Micro-Trains style mounting pad and screw are provided). The locomotive has a working (albeit non-directional) headlight. The tender has a fake (IE, non-operational) back-up light assembly built into it.
The motor is a five-pole / straight-wound "can" (and presumably made by Sagami). Right-rail pickup is provided by the eight right-side drivers (the rest of the drivers, along with the pilot and trailing trucks are electrically neutral). Left-rail pickup is provided by the six left-side tender wheels. A sticky-uppy contact on the forward chassis transfers current to the boiler shell. From there, a short wire soldered to the inside of the shell transfers current to the rear chassis. Said short wire is a bit annoying as it prevents one from completely disconnecting the rear engine from the shell. A long pair of plug/socket-equipped wires (in series with the motor) transfers current up to the headlight. Current is transferred from the tender to the locomotive by way of a pair of stiff wires on the locomotive drawbar (and from said drawbar to the motor by way of a short wire).
The motor bracket and rear gear box are connected by a torque arm (allowing the motor to move up and down in concert with the drivers). The worm boxes and motor are all mounted on coiled suspensions springs. Similarly, each axle is held in place by bearing blocks, and each bearing block has a coiled suspension spring between it and the chassis. The driveshaft design is a bit unusual, what with it extending at a downward angle from the motor to the rear engine's worm box, and then continuing on (also downward) to the forward engine's worm. Said driveshaft consists of metal and plastic U-joint parts. Only one axle per engine is geared (the #2 axle on the rear engine and the #3 axle on the forward engine). All the rest of the drivers are turned solely by the running gear. All gearing is metal. The non-geared #1 drivers on the rear engine are equipped with traction tires (a non-TT driverset is included in the box should you wish to trade pulling power for more pickup).
Overall performance is impressive (especially as compared to Samhongsa's somewhat iffy Cab-Forward models). The locomotive runs smoothly and quietly at all throttle levels. Pulling power is strong (50+ cars on level track) and pickup and current conductivity are very reliable. Having two wires on the drawbar is obviously much better than having just one (although my temptation would be to go ahead and rig up an insulated mini-wire across the drawbar anyway). Slow speed creep is very good, although the top-end speed is pretty excessive (generally the case with Samhongsa brass). The minimum radius for curves is right around 19" (any sharper than that and the pilot truck starts derailing). But even 19" is pushing it, and I'd say that 22" to 24"-radius is probably a more realistic minimum. Overall though, these are gorgeous looking models that run extremely well.
Taking these things apart is a bit arduous (and getting them put back together is even more fun). To remove the forward engine, first unscrew the bar that connects it to the rear engine. Next, find the sliding steam line at the front of the engine (it slides forwards and backwards in a little slot in the boiler shell). Slide it such that the end lines up with the widened section in the middle of the slot, then turn the engine 90 degrees. This will align the little pins on the end of the line with the slot and allow the line to pop out of the shell. Lastly, disconnect the plug for the headlight wiring.
To remove the rear engine, first unscrew the two small screws on either side of the drawbar. Next, unscrew the two small screws underneath the aforementioned bar that connects the two engines together (you won't be able to see said screws until said bar has been moved out of the way). As mentioned previously, a short wire runs from the engine into the shell, so you won't be able to completely separate the engine from the shell (not without first yoinking that wire, anyway).
Note that the rear driveshaft connects to the forward driveshaft with a short plastic connector. One end is keyed and slides into a hole on the rear driveshaft. The other end is pronged and clips to a plastic connector on the forward driveshaft. And as one might suspect, getting that damned thing reconnected is a bit of a nightmare. I've tried it both ways, but the easiest way seems to be slotting the keyed end in first, and then maneuvering the forward driveshaft to grab the clipped end. Have fun!
Reviewed: 2/95 Model Railroader ("Key Imports has done a great job of re-creating SP's mammoth class AC-9 2-8-8-4 steam locomotive as its latest brass model... Our sample model came decorated as number 3800, a coal version. Key also offers another coal burner, 3811, and two oil-burners, nos. 3804 and 3807. Built by Samhongsa in Korea, the model has a fabricated brass superstructure with wire and cast-brass details. The factory paint job and lettering are neatly applied. A can motor drives one axle of each engine, and the side rods transfer this motion to the rest of the drivers. Our sample operated smoothly. The scale 126-foot long locomotive and tender are well-proportioned, and all major dimensions are very close to those in SP specs. Like its prototype, the model's front engine is articulated (hinged) to negotiate curves. This is a big locomotive that will make it around an 18"-radius curve, but it'll look and run better on larger curves. The model should pull about 35 freight cars. If you need more pulling power, there's room for additional weight. However, if you add weight, be careful to avoid overloading the motor and make sure the drivers can still slip if the train stalls. The scale-size dummy coupler on the front is mounted with a screw behind the pilot. It would be possible to mount an MT coupler in this space, but it's side-to-side motion would be limited. There's lots of room on the rear of the tender for a MT coupler pocket. Key's 2-8-8-4 is certain to grab the attention of steam fans, and it will be a beautiful addition to an N scale Espee layout. Price: $830")