Enjoy it. The green is gone, but the piece has not finished telling you things. Stamps, seams and dents survived the lemon; photograph them now, while the surface is bright enough to show every mark. Then write one line and keep it with the object: cleaned with lemon and salt, October 2026, by you. That line decides whether a later owner reads the shine as age or as a Tuesday. Wash it in plain water, dry it warm, and leave it alone. Copper browns again on its own within months. Every further polish takes metal, and the edges of the marks go first.