It works better if you keep all your pictures in the same thread.
The bolt stop is the type used by FN for Browning trademarked rifles.
I don't know if they put it on their in-house actions or if you have a Browning that was rebarrelled by Mr Barnett.
The only reference to W.S. Barnett was on the FN FAL board about a Mannlicher with his name on the replacement barrel. Nobody there knew just who he was or when and where he operated.