From Google.

Check out the website www.artsgunshop.com/. Art Issacson was a Browning gunsmith for over 30 years and worked extensively on saltwood Brownings while employed by Browning. He is now one of the top Browning Superposed, A5,
etc. restorers in the country in his own shop. He has a good article on the saltwood guns on his website. He lists the saltwood years as around 1966 to 1971.