Brian,
it is the relay of the headlights that is missing in the shown place. You may also have a look here:
Flaminia headlight relay Scroll down to "3.4 Fernlichtumschaltrelais". It is in German, but at least you can see how it looks inside. It is the same unit as used in the Flavia, the second last picture shows where it is installed in the Flavia. If you browse the website of the Lancia Club Deutschland, you will find a lot more reports about Flaminia.
Hubert