Piper is held together with four "security Philips" screws located in the battery case. Each screw has a post in the middle, meant to foil use of a standard screwdriver. However....

If you don't have the right bit, just use a large #2 philips head screwdriver: the bit won't go deep enough to get tangled up in the security feature.

Once the screws are out use a plastic spludger to pry open four plastic clips holding the shell together.