Portlight removal.
Your opening port is an original Gray. The parts and complete ports are still available. But I have never seen one bolted through. I don't think that is original. All the Grays on Cherubinis that I have seen are screwed into the core from the inside. Then the outside trim ring is either simply put on with sealant or screwed. On my H37C the trim rings were screwed into the core. Here's a series of three photos that might explain. It happens that it was the one that had previously been replaced, a Bomar, not a Gray. But exactly the same so far as mounting.
Repairing the coring and reinstalling is another story.