The term Derby is an Americanism given to the Bowler
hat as worn by the Earl of Derby at the Derby horse races.
The Hat Shaper Derby is a bit different that the
Shaper Bowler. It has a higher flatter crown than the
Bowler. However, like the Bowler Hat Shaper, the Derby Hat
Shaper also has an inverted
brim. The brim is meant to be flipped-up in your finished hat. The
pictures below show the brim in two different "flipped" positions.