"An opera hat, also called a chapeau claque or gibus, is a top hat variant that is collapsible through a spring system, originally intended for less ...
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spacious venues, such as the theatre and opera house.
Typically made of satin in black colour, it folds vertically through a push or a snap on the top of the hat for convenient storage in a wardrobe or under the seat. It opens with an easy push from underneath." - (en.wikipedia.org 24.09.2020)
