Going through another box of eBay fodder, I came to a Konica FC-1. It's in really nice cosmetic condition, and the lens looks great, but it won't wind or fire. The mirror is in the return position, not stuck. It has a built-in meter and an AE position on the aperture ring, so I thought "dead batteries?" Opening up what I presume to be the battery compartment, I found this mystery object. Anyone have a clue? It seems determined to remain firmly in place.