The Spanish Comb can be seen as part of the movement from the long flapper hairstyle to the numerous bobbed styles which followed in the 1920s.
Just as the Large Bow had controlled a girls hair and provided decoration, so the Spanish Comb could allow minor changes in style without resorting to scissors.
Generally however these combs were worn as decoration and served no purpose. Spanish Combs were most commonly made from imitation or real tortoiseshell .
Above photo about 1917: Age about 17 years old Estimate: born 1900 ± 5 years