The transformer that came in my NH set was metal, turquoise green with white lettering and a chrome handle on top. Almost square, it was roughly 4X 5 inches. Sorry, can't remember the wattage or the number. CORRECTION: I misremembered. The one with this set was black and identified as Allstate.
Guys, in using Lionel transformers with Marx, don't run above 12 volts (not that you'd be much tempted to - it would be flying off the track on the curves no doubt). This was a tip from an old-time certified dealer/repairman when I bought my first Marx from him as an adult.
Have a look at the Marx Colonial house. Notice how realistic the details are: Shakes for the upper story, brick for the lower. The detail shot of the front shows the "wagon wheel" window over the door, accurate shutters, door knocker, mail slot and even a porch light.
