Granger,
I would refer you to;" The British Shotgun", Vol,3,Page 275 [Authors,Baker & Crudgington].From the text we learn that two patents, 18,135 of 1895 and 1847 of 1897 were awarded in the names of, John Robertson,trading as,Boss & Co,for a lock safety device.The illustration of this patent is the same/similar to the posted lock pictures.


Roy Hebbes