SOURCES:

Grail Watch Reference: https://reference.grail-watch.com/movement/sw330-1/

Sellita SW330-1 to SW330-2: https://www.sellita.ch/scripts/calibres/images/IS%2021_Evolution_calibre_SW330-1_vers_SW330-2.pdf

Sellita Barrel Improvement: https://www.sellita.ch/scripts/calibres/images/IS%2025_Amélioration%20barillet%20SW3XX-1.pdf