I need a bit of advice on dismantling these horns. I have two rusty examples and hope to make one good one. I believe they're 1440s, but maybe later 1441s. (Not sure how they differ.) Anyhow, the front dome nut is off. What next? There's another big flat nut behind the aluminium disc (stuck), and there's a ring clamp around the horn body that holds the tin cover in place.