Marathon Clock Slim Atomic Full Calendar Indoor Outdoor Temperature Graphite Grey CL030066-GG-FD-EU1. Marathon has been manufacturing timing instruments for the Allied Forces, and today the fourth generation of the family continues the tradition with a wide range of instruments measuring time, temperature and distance. Marathon watches combine military durability with Swiss engineering and craftsmanship to ensure the highest level of quality and precision. Marathon products are manufactured with the utmost care and go through various quality control measures. This attention to quality is supported by a commitment to excellent customer support to ensure the best possible product experience.