So, the Europeans at the time believed it was the first such achievement, but Dumont somehow was able to get hold of some propellers nobody in Europe heard abou

So, the Europeans at the time believed it was the first such achievement, but Dumont somehow was able to get hold of some propellers nobody in Europe heard about? Seems a bit far-fetched. As I said in another comment, the Wright Brothers were pretty secretive about their works and it wasn't until 1908 that people in Europe knew about them.