a sapphire glass screen used in the device has remained scratch-free after being subjected to being rubbed with sandpaper , keyed and even hit with a hammer .
the test was carried out by cardiff-based iphone repairs specialist iphonefixed.co.uk , which used a sapphire screen from a 38 mm apple watch for its experiment .
two out of the three models of apple watches , which are available to pre-order from today , have sapphire glass screens .