I was under the impression that Val developed the inertia single selective trigger used on the Superposed for most of its life.
Here are the trigger pages from the big 1931 Browning Arms Co. catalog --
1931 Catalog Pg 14.jpg
1931 Catalog Pg 15.jpg
1931 Catalog Pg 16.jpg
When I was at the 1974 Armed Forces Skeet Championships at Ent AFB the gunsmiths in the Browning tent were busy converting many shooter's Superposeds to the mechanical single selective trigger.