It has a closing design based on a glass marble which is held against a rubber seal, which sits within a recess in the lip.
[3] The bottle was designed and manufactured with thick glass to withstand internal pressure, and a chamber to enclose a marble and a rubber washer in the neck.
[4] The bottles were regularly produced for many decades, but gradually declined in usage after the introduction of the steel crown cork bottlecap.
Bilas, a company in Portugal, created a drink named after the bottle design (Pirulito).
However, the marble inside did not seal the liquid; instead it was a normal cap which could be removed without breaking the bottle.