All I see is seems to be a redcolored cowling-ring for a radial-engine, and the only clue here you giving us is that is comming from a 2 seater monoplane, and it also dates back to prewars you said? Well in that time of aviation history it whas when it flourishing at most, and so in that era there came up so many new homebuilder's, manufacture company's and other that these people designed and build well over hundreds of difference variation of this kind of airplane. Whit that pickture's that only shows its a some sort of a cowling-ring for a radial-engine in red color. Well I guess 1/4 of those hundreds difference types of 2-seats monoplane have this part. This gonna be a lot of wild guessing here and there then. Unless you tricking me whit someting that I and we else are missing on the pictures.