This shield can be found on Type 2 buses between the silencer and the engine plating. It prevents that heat coming from the silencer will warm up the plating around the engine-coolant fan. 

If this shield is missing the aspirated coolant air will be heated through the surrounding plating and you’ll risk that the engine will be overheated by the warm coolant air. We notice that on many buses this protection shield has been damaged by fluctuating temperatures, moisture and dirt or have disappeared completely, after that assembly supports have been broken due to corrosion. 

BBT can deliver a good reproduction each from stock.