Automatic cameras of this era can be really ingenious, in the way they achieved a sort of program-mode exposure automation via a
trapped-needle system which is almost entirely mechanical. The "electronics" are usually nothing more than a galvanometer wired to a photovoltaic cell.
I have not looked at a Pen 35EE, but I have worked on Olympus Trip 35s which ought to be roughly similar. Some Olympus cameras have a screw hidden beneath the hot shoe, so if you remove the visible screws from the top cover, and the cover still doesn't slip off, don't resort to brute force.