The Plummer Terrier is a working terrier. It was originally bred by Brian Plummer to primarily be a ratter and hunt vermin. The breed, while unrecognized by any kennel club, is known for its rugged determination and hardiness.
Image credit: Plummer Terrier Club, CC BY-SA 4.0
Adapted from Wikipedia, CC BY-SA 4.0 — https://en.wikipedia.org/wiki/Plummer_Terrier