This is a mid 20th Century, blue, glass soda siphon, made in Czechoslovakia for a French brasserie chain.
The body is slightly conical and vertically fluted, apart from a central circular feature containing the etched wording "Brasseries de la Manche". The engraving on the metal cap repeats that wording.
The clear glass inner tube is intact. On the base is etched "CARAFE FABRIQUEE EN TCHÉCOSLOVAQUIE" ("carafe made in Czechoslovakia").
Siphons were used in cafes, bars and hotels, all around the world and particularly during the first half of the 20th century. They were reusable but had a hard life and eventually became too expensive to use. They're now a collectable branch of advertising because they're usually branded and frequently made from coloured glass.
What condition is it in?
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