Reference 6204, the first Submariner generation, was presented at the Basle Fair in 1954.
This model already featuring many of the now celebrated Submariner characteristics such as the black dial with its typical luminous numerals, the revolving black bezel calibrated to 60 minutes and its legendary shape is however lacking several design elements of later Submariner generations. The most obvious differences are the straight hour hand whereas later models were fitted with the so-called mercedes hand, the lack of minute graduation on the first quarter of the bezel, which could already be found on its successors, and that the depth is not mentioned on the dial, again a feature which can still be found on the models of the actual production.
Reference 6204 is illustrated and described in Vintage Rolex Sports Models by Martin Skeet & Nick Urul, pp. 27 & 28 and in Rolex Submariner by Guido Mondani - Lele Ravagnani, pp. 22 & 23 and pp. 70 - 73.