Which type of adult cell provided the nucleus used to create Dolly?

Dolly, the first mammal cloned from an adult cell, was created using the nucleus from a mammary gland cell.12

This cell was harvested from a six-year-old adult Finn Dorset ewe. To facilitate the cloning process, the researchers at the Roslin Institute induced the mammary cell to enter a quiescent stage by withholding nutrients before transferring its nucleus into an enucleated egg cell. This successful experiment demonstrated that the process of cell differentiation in mammals is reversible, a technique that later became known as somatic cell nuclear transfer (SCNT).123