This is a 1/200 scale Type-M Caquot observation balloon, as used by most combatants in World War I. There is a drainage slot on the bottom fin (since it's hollow, to keep the cost down), as well as a mounting guide-hole with reinforcement. (The mounting hole is conical, so you can drill it out to the size you need. Frequently it works well without modification.)
Also can substitute as a WWII barrage balloon. No basket is included at this scale. This model defaults to polished WSF and works well with the polish.