Kipper Sarnie could be right about the brand. As I said, mine is buried. Added to the above I will mention that the rear of the trumpet is a flat circular flange which bolts onto the cylinder which is faced with a flat circular flange. Onto the flange (about 5 inch diameter) is bolted a curved bracket which bolts onto the chassis rail.
What is it worth? A rough one I suppose about $20 and then take it home and try to get it to work. A good one about $50-70 but that's just a guess.
US part no 342893. Bracket part no 346739.
Good luck at Bendigo
Terry H