Raimey,
As you mentioned, the diskset striker indicates a cape gun or Büchsflinte (BF) arangment, for another set of barrels; possibly for a high velocity cartridge such as 7x65R. I have a Ferlach BF from the 1930s without this sofistication (7x57R), but my Ferlach BBF from the late 1940s has it for both barrels (7x57R and 16/65). BTW both are from same maker (Franz Sodia).
With kind regards,
Jani