Montblanc is not a Swiss company. It was founded in Hamburg in 1908, then as the Simplo Filler Pen Co. (a Berlin prehistory goes back to 1906), and still has its headquarters and its pen production there. Its parent company, however, is the Swiss luxury goods group Richemont, and watch production is based in Switzerland as well, which is why media reports repeatedly describe the brand, wrongly, as Swiss.
In 2008 Montblanc presented the Nicolas Rieussec, its first watch with a movement made in house; the line is named after the inventor of the chronograph. Reporting on it regularly confuses two terms: a chronograph is a watch with a stopwatch function, whereas a chronometer is a watch whose rate deviation has been tested in several positions and confirmed by a certificate. The Nicolas Rieussec carries no chronometer certificate, which says nothing about how accurately it actually runs.
The certification procedure is elaborate and expensive, which is why even well-known manufacturers do without it and instead specify in-house tolerances of around five seconds' deviation a day, figures that at least match the testing standards. A missing certificate is therefore not a defect in quality.