The shield is used on the left arm,held on by two or more straps the forearm is put through. Barge your opponent with shield,keep at arm's length then stabbed with spear underhanded. Therefore,arm straps tend to be substantial.
Centre of shield has strengthening stick held upright by tight strapping, giving strength and rigidity to be take the knock of trying to sweep opponent away from you, keeping him there to be able to stab him.
Hope this helps, don't know where you would someone to advise you in UK. Would presume museum, either military or civilian,as their work entails preservation of old such pieces. Best of luck, Jess.