AM is the caliber prefix for A. Michel SA (also known as Adolphe Michel SA or AMSA), one of the largest Swiss ebauche manufacturers of the early 20th century, founded in 1898 in Grenchen by Adolf Michel (1865–1928) and Jean Schwarzentrub. By the eve of World War I, the firm had grown into a dominant force in Swiss movement production.

A. Michel SA was a founding member of Ebauches SA in December 1926, alongside A. Schild (AS) and Fabrique d'Horlogerie de Fontainemelon (FHF) — the three-firm cartel that came to control Swiss ebauche supply for decades. AM calibers (125, 220, 280, 320 series and beyond) were used by hundreds of watch brands across the volume and mid-market segments. The company was eventually absorbed into the ETA structure following the industry's consolidation in the late 1970s–80s, becoming part of the modern Swatch Group.

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Manufacturer Movement
AM Manual 11.84 mm
AM Manual 11.84 mm
AM Manual 12.8 mm x 19.6 mm
AM Manual 36.05 mm
AM Manual 39.7 mm
AM Manual 41.6 mm
AM Manual 29.33 mm
AM Manual 23.69 mm
AM Manual 23.69 mm
AM Manual 23.69 mm
AM Automatic 19.74 mm
AM Automatic 19.74 mm
AM Automatic 21.9 mm
AM Manual 27.07 mm
AM Manual 26.55 mm
AM Manual 27.07 mm
AM Manual 27.07 mm
AM Manual 27.07 mm
AM Manual 26.55 mm
AM Manual 27.07 mm
AM Manual 27.07 mm
AM Manual 27.07 mm
AM Manual 29.33 mm
AM Manual 23.69 mm
AM Manual 23.69 mm
AM Manual 23.69 mm
AM Manual 38.35 mm
AM Manual 38.35 mm
AM Manual 38.35 mm
AM Manual 38.35 mm