If I had to guess, it's going to have a SM5A or SM500 MCU.
A broken LCD is no problem for the earlier G&W games, the games are very linear and it's easy to find out which output is which lcd segment.
This interview makes me think that the earliest G&W games didn't use any sort of CPU. It will be interesting to find out for sure.http://iwataasks.nintendo.com/interviews/#/clubn/game-and-watch-ball-reward/0/2
"Yamamoto: Izushi-san and I became significantly involved in the series with Game & Watch: Fire, which was the fourth game. At first, we didn't do programming, but made the game through the hardware.
Iwata: In other words, you didn't write programs like you would today, but made the game run through circuit design.
Izushi: Right. That's how we made Color TV Racing 112 and Color TV Game Block Breaker. Just by seeing the specifications for the game, we could imagine what the circuit should look like. So we used a soldering iron to make the prototype of Game & Watch: Fire."