Texas TI-66 Programmable: Toshiba skills to rescue Texas...

[psychlist]

OK, so some time later...the failure of my more modern calculator prompted me to up my game and start using my old TI-66. The LCD display transparent acrylic? cover was foggy/scratched from abrasion, so I flippantly dismantled it. I tried T-Cut Original (car scratch repair cream from my Dad's garage and probably 30 years old), and it removed 90% of the fog/scratches. But something bothers me.

The attached photo shows how I think the "rubber" strip was during dismantling. IIRC it didn't fall off due to stiction or something. The position was very similar to that in OP's own photos. But I can't understand how it can be there functionally. Surely it separates the contacts on the main board with contacts on the display board. But if I keep it there it, the calculator does work. It also feels like I have to press the display module down a bit hard to engage the grey retainers left and right.

Why does it work?