G-Shock CasioNaut or by the official name GAC-2500 and GMC-2500 are the reason that someone at Casio’s Japan office had a bad day, because they accidentally leaked the new model that will be launched soon. It appeared as a listing for a brand new G-Shock series on the official site and sat there long enough for the people to take screenshots.
Everyone talks about it, so in the end it was a good marketing scheme. Intentional or not. It might be the most discussed launch since the G-Shock Nano Ring.
We already have Casioak, now we will have CasioNaut? I actually own the GA-2100, review will come soon and I can tell you from now that is a cool watch to wear. So maybe I will buy the new GMC-2500 in order to have a AP and a Patek that cost way more.
GAC-2500 and GMC-2500 Why is everyone calling it the CasioNaut?
As I mentioned, the new models are GAC-2500 and GMC 2500, and was spotted by a member on forum going by Gary K and it was first reported by G-central. If you look at the case, you will get it instantly. We have that rounded porthole style shape with little “ears” that sticks out on the sides. Basically just like a Patek Philippe Nautilus with the iconic design from Gerald Genta.
Casio doesn’t claim any inspiration from Patek Philippe, or AP Royal Oak, but we all have eyes, we can see the resemblance and honestly we love it! Instead, Casio, point to its own line of G-Shock 5000 and 5600 lines, the square faced original watches to be their inspiring models.
Let’s give them some credit, to be fair the front bezel on the new watches does have that octagonal G-Shock shape that you can recognize from the 5600 line. But the softened curves around it? It screams Nautilus in my opinion.
This is not the first time for Casio to have watches that are compared with popular models. The Casio G-Shock GA-2100 has the nickname “CasiOak” because it resembles the AP Royal Oak. I own the watch , I will review it soon. It’s good, that I can tell already.
Basically Gerald Genta managed to influence two of the G-Shocks’s biggest hits without ever knowing it.
Casio G-Shock GAC-2500 and GMC-2500 What’s inside the watch?
It’s not just about the shape. The GAC-2500 and GMC 2500 have a new module to run on, the 5757, which comes packed with features that go beyond a normal analog G-Shock.
Dial and Hands
The difference between this model and GA-2100 is that on GAC-2500/GMC-2500 you have a full analog display, no digital at all. A subdial positioned between 4 and 5 o’clock position counts 0 to 60 and also doubles as your seconds hand. We also have a date window which has double duty since it also shows which mode you are currently in.
Stopwatch and a little trick with the battery
If you press the stopwatch, it will measure in 1 second increments and it goes up to 30 minutes, and the elapsed minutes are showing up in the same date window. It’s a cool trick in my books.
But, the most interesting trick is the “Second hand sleep” . If you turn this on, the second hand locks itself at the 30 seconds mark and stops moving, which apparently saves a good amount of power. Casio says that it will save battery long enough to stretch from 2 years battery life up to 5 years. Which makes me think that Second hand with all his features consume a lot of power.
We also have a hand shift function that swings the hands out of the way so you can read what’s underneath them. Let’s not forget about a hand and day indicator alignment tool in case magnets or hard knock interferes with hands or date making them to lose the sync.
The watch runs on a single CR1025 battery and yes, it also has light.
Resin and Metal, we get both
I prefer the metal one, I don’t like the Resin models from GA-2100, and for this one I would go for the metal as well.
They are launching the resin and metal one from the first day, something we didn’t have on GA-2100 CasiOak at launch. It’s a good thing, no wait for the metal model.
Here is a list of the watches that will be launched:
- GAC-2500: It has a full resin case and it is the lightest options at 47 grams
- GMC-2500: It has a stainless steel bezel and a resin band. Probably my favourite
- GMC-2500D: Comes in stainless steel bezel and a full stainless steel bracelet. It is considered to be the premium one. It also is the heaviest of the three models at 138 grams.
It’s worth mentioning that if you have GA-2100, the GAC-2500 might not have the Casios’s Carbon core guard case construction. Not really a dealbreaker for me but it is something to keep in mind if it was important to you.
Casio G-Shock Casionaut Versions
It’s expected a total of nine watches to be launched and there are colors for everyone.
- GAC-2500 comes in 4 colors: black,olive green, white and yellow
- GMC-2500 comes in 3 colors: silver bezel with black dial, silver bezel with white dial and gold IP bezel
- GMC-2500D comes in two colors, silver with black dial and silver with blue dial
Casio G-Shock Casionaut when and where can you buy one?
Given the fact that this is a leak, Casio hasn’t announced anything official yet, but we expect a launch in November 2026. The prices are in Japanese currency, but they can give us a good idea of what to expect.
- GAC-2500: ¥20,900 (roughly $134)
- GMC-2500: ¥37,400 (roughly $240), gold IP version at ¥39,600 (roughly $254)
- GMC-2500D: ¥49,500 (roughly $317)
Keep in mind that the prices in Yen are with tax included, so the prices in other countries will depend on currency conversion and local distribution.
Specifications at a glance
| Spec | GAC-2500 | GMC-2500 | GMC-2500D |
| Case material | Resin | Stainless steel bezel, resin band | Stainless steel bezel and band |
| Module | 5757 | 5757 | 5757 |
| Display | Full analog | Full analog | Full analog |
| Dimensions | 46.7 x 44.5 x 12.7 mm | 46.7 x 43.8 x 12.9 mm | 46.7 x 43.8 x 12.9 mm |
| Weight | 47 g | 68 g | 138 g |
| Battery | CR1025 | CR1025 | CR1025 |
| Battery life | ~2 years (up to ~5 years with Second hand sleep on) | ~2 years (up to ~5 years with Second hand sleep on) | ~2 years (up to ~5 years with Second hand sleep on) |
| Stopwatch | 1 sec measuring unit, 30 min range | 1 sec measuring unit, 30 min range | 1 sec measuring unit, 30 min range |
| Carbon Core Guard | No | Not stated | Not stated |
| Colors available | 4 | 3 | 2 |
| Price (Japan, incl. tax) | ¥20,900 | ¥37,400 (¥39,600 gold IP) | ¥49,500 |
| Expected release | November 2026 | November 2026 | November 2026 |
Casio G-Shock Casionaut, Hit or Miss?
I think it will be a huge HIT. We know that G-Shock has a habit of turning internet nicknames into hits and the best proof is CasiOak. Casionaut has the same ingredients because it has a familiar design that is very popular, has a low price tag, G-Shock is a really good watch. All of these makes me think that the watch will be a hit.
Of course, nothing is official yet, they deleted the listing really fast, so we need to treat the leak carefully.
Until Casio makes the announcement themselves , everything is debatable. I really miss the days when Casio launched crazy watches that made history.
Source: Gary post on watchuseek
