"Donegal Tweed" refers to the addition of flecks, either plain or colored, that are added to the wool before being spun into yarn. This pattern originated in southwest Donegal near the village of Kilcar in the 1850s.
These caps are also sometimes called Jeff Caps, Golf Caps or Scally Caps.
Manufactured by Hanna Hats in Donegal Town, County Donegal, Ireland.