Holy crap! It's a 1976 Magnavox Odyssey 300, one of the first home video game systems to use a single dedicated microchip. It plays 3 games: Smash, Tennis, and Hockey (basically three versions of Pong) all with the use of only two knobs (instead of six like the Odyssey 200). Ralph Baer and Magnavox (the creators of the original home video game system, the Odyssey, in 1972) would go on to make several other Odyssey versions, plus even more versions only available in the international market.
This specimen comes in amazingly good condition for a 36 year-old machine, with the power cord, in the original box (with some of the original packing styrofoam)! Who knows if it works, and who cares. These systems are sleek and gorgeous and look better on the shelf than in use.
We have gotten some great old gaming systems here in the past: Atari 2600, Nintendo Entertainment Systems, a boatload of Sega Genesis, Coleco, and even an Intellivision, but I think the Odyssey 300 is the best score of them all so far.
You can see all the Odyssey systems at the pong-story website here.