I'm working on an OM-1 MD that has a weird battery cover that I have not seen before. It looks OEM to the camera body.
Does anyone have any insight as to where this battery compartment came from? Is this a rare variant of the OM-1 or some weird repair that someone performed in the past?
This may not be the explanation for your case, but your photo struck a chord. I once drilled similar holes in the battery cover of my Nikon FE, in order to take wires to an external battery pack which I kept warm in my shirt pocket. This was to use the camera for hours outdoors in the Arctic winter. Keeping the entire camera warm wasn’t an option as it was attached to a 400mm lens.