This review is on Marx's pre-war #999 2-4-2 steam engine. (For those of you who don't hang around the Model Railroader forums, posting reviews is something I frequently do. Since this one's on a "classic toy train" rather than HO scale, it ended up over here where it belongs)
Marx made seven different versions of their #999, with most of them having only simple variations to the front pilot. The first (and rarest) had a pilot with open spokes, but it was found to be too fragile and was quickly replaced with the second version of the 999, which had a closed spoke pilot. The next (and I believe most common) version had a simple, fully sealed pilot with the rivets on what appears to be horizontal braces. The fourth version had the "braces" removed, leaving only the rivets on a very flat looking pilot. The fifth had the Marx logo on the cab instead of the smokebox, and the sixth had no Marx logo at all. The last was made from plastic instead of metal. Versions five through seven used the version three pilot. (information from http://marxtinplatetrains.com/)
Marx's #999 steam engine is built nicely and very sturdily, which is a good thing since many of the owners of these trains were children (and we all know kids can be pretty rough with their toys). The one reviewed here is a version three model, with the horizontal braces across the top and bottom of the pilot. The actual scale is S, but it's designed to run on O gauge track. It's actually pretty detailed for an old toy train, with lots of rivets and piping cast onto the aluminum body. It's very cleanly cast too, with no flash and very few seams. The wire handrails and bell are stainless-steel, which seems to only tarnish instead of rust. The cab is fully open, making room for a crew incase you'd ever want one. The drive wheels are, except for the flanges, very realistic looking, although they're not quartered (which isn't really a problem). There are only two siderods, which are the ones going to the cylinders, so the front drivers are connected to the rear ones only through the gear (which is why a lack of quartering wasn't a problem). The paint seems very durable, and after existing for around 65 years, it only needed a little touch-up in a couple spots. The 999 numbers on each side of the cab are water decals which flake apart easily, so finding one with the decals fully intact can be a little hard. The tender is 100% stamped steel, so it's less detailed than the engine and rusts easily. The coal load is very flat, and the only separate detail part is the stamped ladder on the back. The whole thing is painted high-gloss black, with the yellow New York Central lettering and Marx logos printed on. The trucks are very simple looking with little detail, and the couplers are an odd design (kind of a spring loaded loop, instead of the more common V-shaped couplers). It's still a pretty nice looking tender once it's been de-rusted and repainted.
Aside from a slight wobble, the Marx #999 is a nice running steam engine. It's also very fast, due to a gear ratio of around 6:1. Because the gauge is O but the scale is S, I'll give speed measurements for both. At 13 volts with a 50 watt Marx transformer, the top speed in O was around 130 MPH, and in S, 175 MPH. Low speed running was a little shaky, but it still managed to run at a minimum of 6.5 MPH in O, and 8.75 MPH in S. Through the whole speed range, just about all you can hear is the wheels on the track, some gear noise, and the hum of the AC power in the motor. It's designed so that it can run on O-27 track, but it seems to run better on larger curves. The direction is controlled by an automatic E-unit, which switches when you turn the power off and back on. The power consumption of the AC motor is enough that I wouldn't recommend any less than a 50 watt transformer (it works with my 25 watt American Flyer transformer, but not nearly as well). The drawbar pull is enough to pull more than ten Marx cars, but I wouldn't recommend more than five or six. Pulling too many cars for long could stress the motor out, and it gets pretty hot when pulling four cars for very long. The engine's electrical pickup alone can get flakey with any dirt build-up on the wheels, but with the tender helping it's much better.
Although it may be considered "vintage" now, Marx's pre-war #999 is still a nice looking, smooth running, reliable steam engine. And at only about a third of the price of a new Lionel, it's a great, affordable way to build up your roster.