The first version of the Double Red Sea Dweller (DRSD) was produced in 1967. It is believed that somewhere between 50 to 100 early versions were sent to dealers for promotional use. The helium valve had been developed and the patent had been applied, but Rolex had not yet received final approval. Therefore, these watches were engraved on the case back with word 'Patent Pending.' There are some notable differences between the first version of the ref. 1665 and the later production: (i) the case was thinner; (ii) the case back was engraved with 'Patent Pending' in parenthesis; and (iii) the diver's extension link was stamped 'Pat. Pend'. The double red writing was applied first in white on the black dial and then with red painted over the white paint, so as to highlight the red writing. Both of the lines of Double Red writing are similar in font and size. They read: 'SEA-DWELLER' and under that 'SUBMARINER 2000'. On the few examples that still exist, the red writing has faded to a pink, white or a yellow color. This was due to reaction of the red paint applied over the white paint, hence the dial is often referred to as the 'Double Pink'. The coronet is quite sharp with the five tips of the crown and oval at the base clearly defined. Only a very limited numbers of these dials were produced, and they had 'patent pending' engraved on the case back and stamped on the diver's extension link of the bracelet.