In European caps of the 1920s-40s, its the French makers who seem to have pushed the stylistic boat out. I recently bought another fancy crown cap, with three ridges running from the point of the crown front, to the back. Strangely the cap doesn’t have a snap on the peak, meaning it cap be worn “up” or down. A purely aesthetic belt is fixed under the front of the crown, and has the usual pair of decorative buttons at the temples. The fabric is typical of the era. The brand is “Prima Sport” and was sold by Emile Dupont in Boussu in the French speaking part of Belgium. Glorious!