Louisa built by the Hunslet Engine Co. Ltd. of Leeds in 1877 to works number 195 was one of the first four engines to work in the Dinorwic Quarries. It was named after a child of the owner, Robert George Duff. The first Hunslet named 'Dinorwic' of 1870 was the earliest of a long line of their products to reach the slate quarries of North Wales. There was brother engine to Louisa, George (No.84 of 1877). Larger Hunslets began to work in the nearby Penhryn Quarry in the early 1880's and from 1886 Dinorwic turned over to the larger pattern of locomotive. Later all four pioneer engines were sold, Louisa going to the nearby Glynrhonwy Slate Co. Ltd. before the turn of the century.