Caquot observation balloons were used by most combatants in World War One. They came in several sizes, and the Type-M was probably the most common.
To better match Shapeways' Oct 2014 pricing, the 1:144 model has been split in two and can easily be assembled at the eight pins and holes along its edge. Smaller-scale models are one-piece prints. There is also a mounting guide-hole with reinforcement on the bottom. (The mounting hole is conical, so you can drill it out to the size you need. Frequently it works well without modification.)
The 1:144 model comes with basket and ropes. These are attached by inserting tangs on the ropes through holes in the balloon body with a friction fit. They can easily be removed for storage, or you can glue them permanently into place if you prefer.
Related balloon models: Caquot Balloon
, Parseval-Siegsfeld "Drachen"