The reference 6204 was available with two bezel versions, either without the minute graduation for the first quarter, such as the present lot, or with the graduation for the first 15 minutes. The minute graduation became a standard feature on the model's successors.
The model 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.