Thanks, Gaspare. I tried to show the hallmarks in the last photo above. The silver content mark is 800. There are also two letters, the first one being an 'S'. The second letter is too worn to discern. The third mark is a triangle with something inside but also it's too worn for me to make it out.

The ring is indeed multi piece but you're right: the SA motif is about the right size for a dagger, or maybe a pin. Who knows?

I don‘t think the black is enamel. It is no longer shiny and it's not hard enough to be enamel. Either way, it's a cool ring and it is pretty old.