beaver felt

Two-cornered hat (bicorne), c. 1789 - c. 1810.

After the French Revolution (1789), the three-cornered hat (tricorne) – the symbol of the previous government known as the Ancien Régime – fell out of favour. However, a large two-cornered model, the bicorne, remained fashionable until around 1810. It was also called a corsair after its most famous wearer, Napoleon Bonaparte, who came from Corsica. This hat is made of beaver fur felt, which was expensive and very popular. 

(Rijksmuseum)