mGARANDEUR1 wrote:
Sapphire crystal is the hardest crystal available for watch glass. It is quite difficult to scratch. The AR (anti-reflective) coating that is on both sides is also very durable, but probably will come off eventually on the outside of the lens. The steel on the watch is going to get scratched long before the crystal does. I wouldn't worry about it.
A proper sapphire crystal is a sign of a quality watch. Mineral glass or acrylic will quickly become covered in scratches and are found on cheaper watches.
As mgrandeur1 states, the AR coated it pretty tough, but it is possible to scratch.