Joan Rivers enamel flower bracelet

Love, love, love this, but I’m not really into wearing bracelets. Looks GREAT, but I have no idea why it’s tarnished on the back (ONLY) — only noticed just now (very certain the metal isn’t sterling silver), as I’ve kept it stored in a jewelry box. Colors are red, white, yellow, purple, pink. Magnetic closure works great, is nice and strong.