ROLEX, STEEL CORNINO 'GMT-MASTER' UNDERLINE WITH GILT DIAL, REF. 1675

The 'underline' was printed on the dial by Rolex to show the transition from radium to tritium used on the indices as a luminous material. There are three typed of gilt dials seen on reference 1675, the present one being the second variation and also the most frequently seen with the underline.