Most of the early bottles had corks. Think of wine bottles. Why do they store them on their sides? If the cork dries out they shrink, so they lose the seal. If the bottle has to be stored on it's side there's no reason for a flat bottom. If you look a early gin bottles they're square. Why? Less damage when shipping, because they fit, nice and tight in a wooden crate with no room to bounce around in.
i think you nailed it. after cleaning it up some more, i removed the layer of what i thought was some type of metal that was stuck tight around the neck, well, its just old rubber. i believe i found an exact pic, but its only from the top view and grainy. either way, its still old as hell, clearly handmade, and somehow remained unbroken.