Casio leaks upcoming G-Shock GAC-2500 and GMC-2500 “CasioNaut” watches with PP Nautilus-like shape, module 5757 functions revealed

Thanks to Gary K for discovering the all-new G-Shock GAC-2500 and GMC-2500 series, which are expected to be released in November 2026. Nine new watches from these series were briefly listed online at Casio Japan in an apparent error.

Like the popular GA-2100, the GAC-2500 and GMC-2500 watches bear a somewhat undeniable similarity to another classic luxury timepiece (Patek Philippe Nautilus) which has earned them the nickname “CasioNaut,” although the G-Shock 2500 watches retain an octagonal-shaped front bezel based on the classic G-Shock 5000 and 5600 lines. For the first time, G-Shock is launching a new series in both lightweight resin versions (GAC-2500, 47 grams) and metal-covered versions (GMC-2500) with a stainless steel bezel and resin band, as well as GMC-2500D models with a stainless steel bezel and stainless steel band. Unlike the GA-2100, the GAC-2500 does not appear to have a Carbon Core Guard case.

The 2500 has a full analog display, including a 0-60 subdial indicator and a date display that also displays the modes. In timekeeping mode, the subdial acts as the second hand, and there is also a stopwatch mode with a measuring unit of 1-second and 30-minute range. The elapsed minutes in stopwatch mode are displayed on the date display. The optional “Second hand sleep” function keeps the second hand fixed at the 30-second position to conserve battery life. According to Casio, enabling this feature can extend the battery life to approximately 5 years instead of the usual 2 years. There is also the hand shift function to clear the hands out of the way of the indicators, and “Hand and Day Indicator Alignment” to manually adjust the hands and date indicator that have been misaligned due to magnetism or impact. The dial has an LED light with a 1.5-second duration, powered by the upper-right button. The watch runs on a single CR1025 battery with an approximate life of about 2 years (assuming one illumination per day and disabled “Second hand sleep”).

The full resin GAC-2500 measures 46.7 x 44.5 x 12.7 millimeters and weighs 47 grams. The metal-covered GMC-2500 with resin band measures 46.7 x 43.8 x 12.9 mm and weighs 68 grams, and the GMC-2500D with a stainless steel band measures 46.7 x 43.8 x 12.9 mm and weighs 138 grams. There will be four GAC-2500 models in black, olive green, white, and yellow, three GMC-2500 models (silver bezel with black dial, silver bezel with white dial, and gold IP bezel), and two GMC-2500D models (silver with black dial, silver with blue dial). The price range in Japan is ¥20,900 for the GAC-2500 models, ¥37,400 for GMC-2500 (¥39,600 for the gold IP model), and ¥49,500 for GMC-2500D.

The English instructions for module 5757 can be viewed as a PDF file at casio.com.

View Gary’s original post at watchuseek.com and see all the upcoming GAC-2500 and GMC-2500 models.