Leaving cert results done in 1988 criteria for new job question

The company shouldn't be asking for leaving cert results from nearly 30 years ago tbh. I don't even remember what I got and that was 16 years ago.

Go back to them and accept the offer but tell them you don't remember what you got in your leaving cert and ask whether your experience and education since is sufficient.

If they tell you that you absolutely have to meet the criteria and to go get a copy of your transcript, hand it over to them. If they withdraw the offer, so be it. No harm, no foul.

Just don't quit your current job until you have a signed contract from the new one. You have nothing to lose by proceeding to accept the offer from the new company.