Metal
From article Tinbe-Rochin on Black Belt Wiki:
The Tinbe Rochin is a traditional Okinawan (Japan) Kobudo weapons combination consisting of a shield (tinbe) and short spear (rochin). The shield was often made from a large turtle shell or a farmer’s conical straw hat (that used the straw in order to trap an opponent’s weapon).
This weapon can be found in the Kubudo training (weapons training) of many different Karate styles. However, the Tinbe Rochin is less utilized than other better-known Kubudo weapons such as the Bo, Nunchaku, Sai, etc. The Tinbe Rochin is also used in weapon katas such as Kanegawa No Tinbe Kata. As with other sword/spear and shield weapons, the shield is primarily used to block/defend against oncoming strikes . The rochin/spear is primarily used to thrust and slash but is also used to block. Likewise there are some strike/attack techniques for the Tinbe or shield.