It has a special design for deep-sea swimming and, like the Turn-o-graph, is equipped with a bezel for recording time.
This "like the Turn-o-graph" shows that for Rolex, the rotating bezel was of a wide profile, and was originally developed for civilian watches. As can be seen from the patents for the bezel, which indicated in advance the manufacture and materials of the bezel (including gold). There is zero information about diving in the Rolex patents CH305177A & CH312285A.
But Jean Fiechter was more focused on creating a deep-sea diving watch, rather than a civilian one with a gold bezel for timing the time of a banal telephone conversation. His patent CH322328A just confirms this.
For Rolex, it was more important to release a Turn-o-graph and a Submariner with a bezel like the Turn-o-graph, but Blancpain's goal was to release a deep-sea watch for the French Navy.
Out of all this, for me personally, Blancpain was the first to release an honest diving watch. And Rolex has adapted civilian watches for scuba diving. And it doesn't matter that the 6204 case was released on 02.53. The important message is that J.Fiechter was more focused.