Thank you for your insights and that link - Bing's thunderbolt may be legionary, although the Fulminatas I've seen have been in rectangles. The Side countermarks with thunderbolts (I've seen a couple others online) are in circles, like mine, and neatly applied to the helmet. I just don't know. I had not heard of that article. Certainly Side had a lot of countermarking going on (silver and AE), and would be worth a study. It'd be nice if something's been discovered since 1906, but what's a hundred years in the world of ancient coins?
