Appears to be a rat terrier. Great little dogs. I have a half chihuahua and half rat terrier. She can dispatch a rat in two seconds . I saw her pull one running up a wall and shaking it to death. Or I’ve seen her crunch down on their backbones breaking their back. Very fast and efficient hunters. And very loving, smart loyal pets.
I have a little black and tan dog who is a chihuahua/dachshund mix. He is a great ratter, and has the highest prey drive of any dog I’ve ever known. A squeaky toy kicks him into overdrive.
He is also a frisbee expert, and will catch and retrieve to the point of total exhaustion.