On top of its earlier gains, the stock just jumped 11% on earnings. Signet Jewelers (SIG 4.84%) isn't a household name among investors or even shoppers, but you likely know some of its brands. The company is the world's largest diamond jewelry retailer and owns banners like Kay, Zales, Jared, and Blue Nile, among others. While the jewelry market has been volatile in recent years, swinging back and forth amid pandemic highs and lows, the stock has been a winner over the last five years, up more than 400% dur ...