lancaster,
The Herkules guns are certainly a very interesting design.
The photos you posted here are also very interesting, and thanks for posting them.

The O/U Herkules action shown in an old advert in Hatari Times #7, has a much different set of locks to the O/U which you've shown here.
The one in HT has the more usual tumblers powered by V springs, on a trigger plate style action.