Vintage 20mm Hamilton Masterpiece 22J Mechanical Wristwatch Movement 770 USAProduct Description Item: Wristwatch Movement Brand: Hamilton Model: Masterpiece Movement: Mechanical Jewels: 22 Caliber: 770 Country: USA Gender: Unisex Product Measurements Diameter: 20mm Diameter of dial: 29. 5mm Length: 22mm Width: 20mm Product Condition The Hamilton Caliber 770 is widely considered the pinnacle of American made manual wind wristwatch movements. Introduced in 1955, it was Hamilton's flagship movement until the Lancaster,