What refrigerant is in there?

[ujourdan]

I bought this car (1991 300D 2.5Turbo) a few months ago. It seems that the air conditioner could use a bit more refrigerant. It is still cooling but when it is really hot, it is not cutting it. The sign in the engine compartment says that is has R12. The service records that came with the car say that it was topped of by a Mercedes dealer a year ago with R134A Freon. Isn't R12 Freon and 134A a replacement? I'm a bit confused here. How can I tell what is actually in there?

Thanks .. Udo