Zenith 661

	Brand:	Zenith
	Family:	Zenith Elite
	Height:	3.28 mm
	Jewels:	26
	Reserve:	55 hours
	Frequency:	28,800 A/h
	Winding:	Automatic, Bi-Directional Automatic Winding, Central Rotor Automatic Winding
	Diameter:	25.60 mm (11.5 ligne)
	Complications:
	Hands:	Central Hour Hand, Central Minute Hand

Distinguishing Technical Characteristics
Ultra-Thin Central-Rotor Automatic Central-Rotor Automatic Clockwise Balance Cock Balance at 1:30 Barrel at 7:30 Central Rotor
Production: 1994 –
1910s	1920s	1930s	1940s	1950s	1960s	1970s	1980s	1990s	2000s	2010s	2020s

Cal. 661 is an ultra-thin automatic movement from Zenith. Closely related to other Zenith Elite movements, Cal. 661 lacks any complications, including the seconds hand, and is reduced in height to just 3.28 mm. The similar Cal. 660 has a date display but is not used in any known watch model.

Cal. 661 was one of the original Elite movements launched in 1994 but was rarely seen since. The original Elite “Série 6” model was a limited edition of 250 in platinum and was introduced at the Basel Fair in 1994.

Technical Aspects of the Zenith Elite Movement

The basic Elite movement measures 11.5 ligne (25.60 mm) diameter and most models are under 4 mm thick, despite a central automatic winding rotor and date complication. A few models used a larger main plate to move the date window outward or to support complications like a running 24 hour ring. The thinnest Elite movement is the hand-winding Cal. 650 at 2.83 mm and the thickest and most complicated is the large Cal. 687 at 6.20 mm.

Unusually, many Elite movements (apart from the 660 and 670 lines) feature small seconds at 9:00, a distinctive feature that differentiates the watches that use it. Some, however, feature central seconds, an adjustable 24 hour hand, a power reserve indicator, and other complications.

All Elite movements use an annular Glucydur balance wheel with a self-compensating balance spring and fine micrometer screw for adjustment. The automatic winding rotor is mounted on ball bearings like the ETA 2892 and originally included a tungsten carbide element for higher winding power. Most Elite movements boast 50 to 55 hours power reserve and all operate at 28,800 A/h.

Zenith Elite 650 and 660: Ultra-Thin

Cal. 661, a simple two-handed version, was one of the original Elite movements. The hand-winding Cal. 650 and 655 were soon introduced as well. All of these movements were advertised as “ultra-thin” by Zenith.

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