Opera hat

Typically made of black satin, 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.

[2] On May 5, 1812, London hatter Thomas Francis Dollman patented a design for "an elastic round hat" supported by ribs and springs.

The rest of the hat "is left entirely without stiffening," and is kept in shape by ribs of any suitable material "fastened horizontally to the inside of the crown," and by an elastic steel spring from three to four inches long and nearly half an inch wide "sewed on each side of the crown in the inside in an upright position."

Then packed up for travelling, "the double ribbon fastened under the band is to be pulled over the top of the crown to keep it in a small compass.

"[3] Some sources have taken this to describe an early folding top hat,[4][5] although it is not explicitly stated whether Dollman's design was specifically for male or female headgear.