I have seen the story many times about how Browning only started the design and it was perfected by Diudonne Siave (sp)?. I don't think that is right.
On page 301 of the book about Browning, there is a picture of the prototype hammerless Hi-power, then on page 302 is the hand made prototype with exposed hammer. It also gives the date the US patent was issued to Browning.