This is a kind of cool looking game, and is fairly rare (although they've been popping up kind of frequently lately, even two boxed ones... Game play is similar to Galaxian and such (unlike Defender, like the name suggests). On the inside of the game the number HP-839 is written on the circuit boards, not sure if that's a model number, or just a circuit board part number... First snap-together tabletop game I've seen, no screws involved to open it up (but there are screws holding things together on the inside).