IF YOU'VE GOT it, flaunt it. With fully-transparent sapphire cases, every intricate movement inside a luxury watch is naked and visible to the eye. And today, watchmakers' ability to produce sapphire cases on a much larger scale may herald it as the next coveted feature of timepieces.

In January, Swiss watchmaker Hublot unveiled the Big Bang Unico Sapphire, an all-sapphire case flyback chronograph available in a limited edition of 500. And though the production number is capped, no other brand has so far made a full sapphire case watch on such a scale, confirming that the mass production of a watch encased fully in sapphire is possible.

Sapphire, which is transparent and nearly as hard and scratch-proof as diamonds, has been widely used in highend watchmaking since the mid-1980s. A sapphire crystal cover for the front and back of the case has become a standard feature of luxury timepieces, guaranteeing protection and a clear reading of the time.