Casio's carbon-fiber MTG-B4000 now rumored to get a new limited-edition this year

A new MTG-B4000 registration has surfaced in an international certification database, according to Great G-Shock World, though what the entry represents is not yet clear.

The site reported the finding on Monday and tied it to two possibilities. Casio has released a limited MT-G at year-end in the past, doing so in 2023 and 2024 before skipping the tradition last year. Alternatively, the registration could belong to one of the G-Shock 45th-anniversary models expected from autumn 2027. Great G-Shock World considers the year-end limited MT-G the more likely of the two. The blog does stress that nothing is confirmed.

Now, fans are speculating that this year's model could be based on a rainbow finish, since G-Shock's limited MT-G references have often had that treatment. Great G-Shock World is explicit that no evidence supports this for the MTG-B4000 specifically. It does mention that only that the GMW-BZ5000D full-metal series received a rainbow model this year, which makes the idea much more plausible for the MT-G without directly confirming it.

The MTG-B4000 itself launched in May 2025 as Casio's first commercially available G-Shock with a frame developed using generative AI. The exterior uses stainless steel with laminated carbon and glass-fiber sheets over a carbon-fiber-reinforced resin case, with a stainless caseback made through metal injection moulding and a sapphire crystal on top. It uses Casio's Module 5743, with Multi-Band 6 radio reception, Bluetooth pairing through the Casio Watches app, and Tough Solar charging.

The most recent addition to the line, the MTG-B4000B-1AJF, launched in June at ¥176,000, roughly $1,106. It has red accents with a carbon-layered frame.

Great G-Shock World says it will follow up once further details on the certification entry show up.