When JMB’s last design was finished it was overly complicated but the basic elements were there. Upon JMB’s death at FN, Saive was designated to finish the design, simplify it, & ready it for production.
Saive’s final design changes were completed in 1935, ready for the French government new pistol trials. Ultimately the French declined the P35, but others saw the brilliance of the melding of the two designers efforts. It remains a classic 9mm pistol. Saive later designed the FN FAL.
The rest is history.
(On a person note, the “teeter-totter” trigger sear design is one of the worst ever designed. The BHP is the only auto that has this setup, & nobody has ever copied it because its just awful.)