This is a neat little hat.
Made in the 1950s in England and labelled A Marten Hat, it features a wired frame covered with off-white fabric which has then been entirely covered with layers of off-white tulle. It has a wired "cap" section to help keep the hat in place but the previous owner added a hat elastic for extra security.
Because of the design and the fact that the wire frame has some flexibility this hat is one size fits all.
Good. It shows little wear. There is a crease in the crown but it looks like it may always have been there.