Iron shield boss with copper-alloy flange rivet(s); wood remains

Shield-boss, only just over half of it survives. Height 8.3cm, diam 15.5cm. Carinated boss with stud on top, and ridge carination below convex dome, and above nearly vertical waist and sloping flange. Whole boss badly corroded and covered in sand: one detectable rivet has bronze shank and whole section of shield-board, and bronze stud head just visible. The section of wood is about 7mm thick and the grain appears to go one way - i.e. board is a solid piece of wood and not laminated.