Our long-term aim is a detailed study of the Arms & Armour in the Wallace Collection, London, which contains over two thousand items and is one of the most important collections of European arms and armour in Europe. Of course, many medieval helmets were altered during their working lifetimes. It is not always easy to determine whether a visible alteration was contemporary or the work of a 19th century restorer. Since Sir Richard Wallace and his father bought much of their collection from dealers, the latter is always a strong possibility. Our investigations at ISIS have demonstrated that TOF-ND can provide much of the information that metallography can (but non-invasively) we hope to explore the alterations of some helmets. Distinguishing between medieval metal and Victorian (puddled) wrought iron would give the museum this valuable information.