Blancpain

Le Brassus, Switzerland. Founded 1735. Swatch Group.

Le Brassus maison tracing its origins to 1735, known for the Fifty Fathoms dive watch and the Villeret collection.

Three groups: model (4 digits, optional letter) then configuration, e.g. "5903 1110 063A"; zero-padding varies (063A vs 63A).