A five-tube, five-band radio covering 150 kHz--30MHz. It has an internal speaker, a BFO switch for CW/SSB, and a receiver/standby switch for use with a ham transmitter (uh-huh).
One site I've found on the Web, electronic/tomsworld, says that this Zenith M660A is the only communications receiver that Zenith made other than its Transoceanic series -- I haven't come across other info corroborating this, but if that's so, that's pretty interesting. Regardless, it's a really nice "cheapie" tabletop set, along the lines of several cheapie Hallicrafters radios of the day. One nice thing here is its 4-inch band spread dial, far better than those provided on its Allied/Heathkit/Realistic contemporaries.
I love the wording on the left-hand column of the dial: "LONG WAVE FAA WEATHER" / "BROADCAST" / "WEATHER MARINE & AMATEUR" / "AFTERNOON & EVENING" / "ALL DAY". And on the tuning dial itself, there are the markings, "DISTRESS CALLS" / "SHIP TO SHIP" / "MARINE & WEATHER", and so on.... Markings like these really got a kid's imagination going!