Um, Chris, y'r Polaroid MP-4 shutter has no diaphragm, so is somewhat of a poisoned gift.

I know this question might be taken as insulting, but it has to be asked. Your MP-4 shutter has two levers sticking out of it. One has a button at the end with a silver face. This fires the shutter. The other, whose little button has a black face, flips between two positions: shutter open (can't be fired) and shutter closed (can be fired). Are you sure it is in the "shutter closed" position?