Supra shows the moves on the LCD, are you sure? The manual says it's for total time. There's no videos of Supra on youtube, but there's one old video of Royal and I didn't see moves shown on the LCD either.

For that reason, I was (still partially am) suspecting they went for the cheap solution and used a wristwatch or stopwatch IC.

Can you show a photo of the front side of the LCD daughterboard?