Hi,
I agree with Nicole. It is clearly a 1950s shape, and is covered with 1920's or earlier dress remnants. It does not look 1920s at all, as the person who made it for a costume had no real sense of fashions of that decade, but after all... it was only for a costume so we forgive the maker! The side feather is just crudely sewn on too.
For some reason, many early and mid 1950s styles seem to be called Flapper hats by many sellers, when none of them ever really look 1920s. Oh well!
B