Pork Pie Hat’s shape has evolved over time; however, the distinctive feature that makes a hat called a Pork Pie Hat is a crease running around the inside of the crown top. This feature has remained intact over the years.
Initially, the Pork Pie Hat was a small rounded hat with the brim slightly curled up. This design had a shallow domed crown with a distinctive crease. The crown even had a ribbon around it and was decorated with feathers on one side. It could be made from various materials such as felt, straw, canvas, and so on.
Later, the Pork Pie Hat was redesigned from Fedoras by stiffening its brim and flattening the crown, unlike the domed crown. Finally, during the Great Depression, Pork Pie Hat came with telescopic crowns that would slightly pop up when worn.