Given the fact Harry Hill used to take the rise out of it, I imagine it is NOT a glass one. It would be a bit insensitive if that was the case and no doubt warrant complaints.
We had a surveyor at work with an eye like that. I always thought it must be handy in his job cos he could talk to the client AND have a look around the property at the same tim!!
Not just a wonky eye for his part in Corrie, he has a wonkey eye for his Doctor Who character too. Poor guy I read in the local paper his 14 yr old daughter died and he lost his wife to cancer.