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. Many items of plate armour can be investigated non-invasively by metallography, depending on the shape of the plates. However, many helmets have rolled edges and so metallography is difficult without taking samples. so only neutron diffraction is an ethical method of analysis. There are a number of helmets which stylistically might be products of the Imperial Workshop at Innsbruck, but their makers’ marks have not survived. Characterising them as having microstructures of tempered martensite (in the late 15th century) would be strong evidence for their having been made in Innsbruck.