Hi Mc,
I have several Hohner Piano 36s. I took one apart about six weeks ago.
I can say that a caulk-like sealer is applied between the bottom cover and the body in several locations. Just a dab at the corners and at the peak of the “roof line.” This caulk must be overcome to get the cover off. I don’t remember how I did it, but the cover will come off with some persuasion.
Regards,
Lowboy