Notes: This watch model is the very first in the Submariner family. It was made available in 1953, and it was only manufactured for one year. According to Rolex, it is the first publicly available watch in the world with water resistance at 100 meters. At the time of the Submariner’s initial release, scuba diving was still a very new sport, and the concept of a watch specifically designed for underwater use was still just in its very beginning stages. The Submariner’s 6204 was derived from the reference 6202 Rolex Turn-O-Graph which was released shortly before the Submariner made its debut. Based on serial number records, among these three early Rolex Submariner references – the 6200, 6204, and 6205 – the earliest serial number case engravings appear on reference 6204 watches that have caseback stamps from II.53. As far as the reason behind this numerical inconsistency, many believe that Rolex started development of the reference 6200 first; however - for some unknown reason - the watch was not ready for production by the time Rolex wanted to launch their Submariner line, and so the 6204 was released first, quickly followed by the reference 6200 and 6205.

Interestingly there are a number of dial variants for the 6204s. Many lack the "Submariner" label. Note that the model number (6204) is what makes it a Submariner, not the label on the dial. A number of submariners were also made for the British Sub-Aqua Club and some dials feature the inscription 'sub-aqua'. There are a number of other variants available for the 6204s with regards to text. Some feature the words certified chronometer, some have the oyster and perpetual spaced far apart. The reference 6204 Submariner was able to achieve its 100 meter water resistance with the help of Rolex’s screw-down winding crown and extra-thick “Tropic” acrylic (plastic) crystal.

Mechanism: The A260 was used in the 6202, 6204 and 6205 Oyster series in the 1950s. It is a fairly obscure mechanism compared to some of its mass-produced contemporaries. It is an automatic (self-winding) mechanism. Both the A260 and A296 were developed at the same time. Neither one is superior to the other. They just have different form-factors, with the A260 being designed for slimmer cases than the A296. Both are COSC certified as chronometers.

Family Notes: The Rolex Oyster Perpetual Submariner is a line of sports watches designed for diving manufactured by Rolex, known for their resistance to water and corrosion. The first Submariner was introduced to the public in 1954 at the Basel Watch Fair. The Rolex Submariner is considered "a classic among wristwatches", manufactured by one of the most widely recognized luxury brands in the world, and due to its popularity has become the subject of massive counterfeiting. The Rolex Submariner is part of Rolex's Oyster Perpetual line. See a copy of the 1957 Submariner magazine advertisement.

The Submariner model went into production in 1953 and was showcased at the Basel Watch Fair in 1954. The assigned case reference number of this first Submariner was either 6204 or 6205. It is unclear which model came first; in any event, the two watches are nearly identical. Neither has the distinctive "cathedral" or "Mercedes" hands now so strongly associated with the Submariner line. Rather, both of these early submariners have straight "pencil" style hands. Few, if any, of the 6205 watches bear the name "Submariner" on the dial, a major distinction of modern Submariners. Some 6204 models have the Submariner logo printed below the center pinion, while others have the logo blacked out. It is believed that there were unexpected trademark issues connected with the name "Submariner" at the time the 6204 and 6205 were released, accounting for the inconsistent use of the Submariner mark on these early Submariners. Trademark irregularities notwithstanding, both the 6204 and 6205 are designated Submariner models in Rolex product literature.

From Wikipedia