The Submariner Comex model, ref. 5513 and 5514, was specifically developed by Rolex for Compagnie Maritime d'Expertise or COMEX, a professional diving operation for the oil industry. The gas escape valve was designed to release excessive helium pressure from the case during the diver's decompression periods.
The reference 5514 is amongst the rarest of all Submariner models, according to literature less than 200 examples were made and sold exclusively to COMEX. It was never available to the public.
The model is illustrated in Rolex Submariner, by Guido Mondani-Lele Ravagnani, pp. 158-161.