Who is slim?

Slim is the jerkline skinner at the ranch, Slim is a seemingly ageless man who carries himself with great gravity. He gives Lennie one of his new litter of puppies to care for.Slim is wise and fair. He is known as the "prince of the ranch." He decides things about the men and crews. He is soft spoken and a good judge of character, "I can tell a mean guy from a mile off."