I did a search for "vintage teardown" on youtube and got a few interesting hits. mr1968geek has several handheld game teardowns, including a couple that I've bought- Entex Space Invader and Coleco Quiz Wiz. My Space Invader has a National Semi COP444L, but his has a TI chip, likely a TMS1x00 (MP1211). The Quiz Wiz has completely different markings, but that's a custom chip, so I'm not surprised. He also has vids of Coleco Digits (like Comp IV) with a GI AY-3-8400, Entex Electronic Baseball with a TMS1000 (MP0914), Videomaster Colourscope TV Games with a National NS/743 MM57105N, and an Invicta Electronic Mastermind with a Rockwell MM75 (the smaller PPS-4/1). That's a nice selection of chips, but unfortunately no MP3403....