I already asked this question in Reverse Engineering StackExchange more than one year ago. Since then I got no answer and I have tried to search again in google and so with no success.
I have seen that reverse-engineering it is more for decompiling, programming, etc. I hope that posting the question here, it is more probable that someone could help.
The unknown chip: IC reference: 25072478 REV D 9119 CCA
The main microcontroller:
As I explained in the original question, this is from an Opel LCD dashboard from late 80's. I have seen pics from this chip with a fabrication date as old as '89.
We are struggling to gather information about this chip, as it is one of the key components of the dash, because it stores mileage inside.
My complete research and information, including many tests, more PCB pics and videos is here: https://www.clubgsispain.com/showthread.php?t=37150
Any information will be really welcome, because as you can see months keep going and I am starting to consider it impossible.
NOTE: About schematics I got them following the traces in the PCB so there may be mistakes.