Broad Black Brimmer was an Irish Republican song on an album of political/revolutionary music. The album came from a little record store in Cambridge, Mass. The lyrics I recall are It's just a broad black brimmer with the ribbon frayed and torn, By the carelessness of many a mountain breeze, An old trench coat that's all battle-stained and worn, And the trousers almost threadbare at the knees, A Sam Brown belt, with a buckle big and strong, And a holster that's been empty many's the year...

Thank you! This song has been stuck in my head, incomplete, for decades.