Monta M-23

The M-23 is Monta's GMT-capable caliber, introduced to power the brand's dual-timezone models — most visibly the Skyquest GMT (circa 2023) and the Noble Voyager (2024). Earlier documentation places the designation on a Sellita SW330-1 or ETA 2893-2 base with a 42-hour power reserve; current production rests on the Sellita SW330-2, which Sellita announced in July 2020 and which extended the typical power reserve to 56 hours.

The SW330 family was itself engineered as a dimensional drop-in for the ETA 2893, the industry's thin-GMT workhorse used for decades across the Swiss industry. The M-23 sits squarely in that lineage: Monta adds rhodium-plated rotor finishing and dial-side adjustments but leaves the escapement geometry unchanged. The GMT implementation is the 'caller' (independent hand) style — the 24-hour hand quicksets separately from the main hour hand, which many travelers prefer over the more common 'flier' GMT.

Because it is built on a Sellita base, the M-23 can be serviced by virtually any watchmaker with access to standard Swiss parts, a practical consideration Monta's marketing openly emphasizes. The movement is not widely licensed beyond Monta's own lineup, making it effectively an exclusive branded variant rather than a broadly distributed caliber.