I think I know what is going on. There is a white, putty-like substance that is used in several locations to seal the cover to the body. On my Piano 36 (gold trim), it was located in the four corners and at the ridgeline at both ends.
The cover does not fit perfectly, so there areas must be sealed up. At least this is what I found on mine.
So I would recommend prying evenly and gently and see what happens. There are no hidden screws or tabs to the best of my knowledge. I took mine apart several months ago.