Atlas imported a couple of different Plymouth WDT's back in the early days of N scale. The first (released in 1968) was manufactured by Mehano (Yugoslavia). The roadnames were Santa Fe, Great Northern, Burlington, and Pennsy. For reasons unknown, Atlas dropped the Mehano version fairly early on and subsequently contracted Roco (Austria) to manufacture this second version starting in 1972. Roadnames for this version were Santa Fe, UP, BN, Illinois Central, and Soo Line. This model vanished from the universe circa 1983 when Atlas discontinued production on their entire line of Roco-made locomotive models (coinciding with their new relationship with Kato).
The shells between the two versions are virtually identical, although they do have their subtle differences. The easiest way to differentiate one from the other is to look at the bottom. The Roco models are stamped "Atlas - Made in Austria", whereas the Mehanos have no markings at all. Unfortunately, they're both pretty useless (both in terms of looks and performance).
The motor is a 3-poler and quite small (well, it would have to be, now wouldn't it?). All wheels are geared and provide pickup (there are no traction tires). A non-directional headlight is mounted to the front of the chassis. The couplers are chassis-mounted Rapidos. The worm is metal, whereas all the rest of the gearing is plastic.
Like the rest of the tiny 0-6-0 type locomotives available in the early days of N scale, performance on this model is generally pretty awful. Yes, it actually runs fairly quietly. And yes, it'll run around a circle of track at full throttle fairly reliably. But, don't ask much more from it than that. The simple 3-pole motor doesn't provide much subtlety in the way of throttle response - IE, it's either not moving at all or it's moving fast (and with the top-end speed being worthy of the Indy 500). The main problem though is weight (or lack thereof) - it's simply too light for pickup to be effective, so stalls and overall jittery behavior are the norm (and forget about getting it through a turnout). Given said lack of weight, it's also not going to be able to pull much (if anything). Worse still, it has a distressing tendancy to derail for no apparent reason. So, basically another unusable industrial switcher from the early days of N scale. Yay.
To remove the shell, simply pry the sides apart to free it from the plastic tabs on the chassis.
Reviewed: 4/73 Model Railroader ("The Atlas N scale version is well proportioned but slightly oversize in order to accommodate the drive system... The ready-to-run N scale model has a one-piece cast plastic superstructure which is painted and lettered for one of five schemes: SF, UP, BN, IC or Soo. We found no record of any of these particular railroads' owning these small units, but the railroad names will probably be more popular than to use the names of little-known contractors or other concerns... The model's frame is a zinc alloy casting with... drive to all six scale 43" drivers. The all-metal wheels have .035"-deep flanges and the wheel check gauge is .311". The motor is a new 3-pole 12-volt DC permanent-magnet type, according to the manufacturer, A small cast weight fills the engine compartment and the front headlight is illuminated... The model will handle about 17 to 18 freight cars... Our test sample ran smoothly... It has a high minimum speed... The model is quite light, so it doesn't take much dirt or grime to produce poor electrical contact. Price: $8")