Zenith 18 1/2''' N.V.S.I. lép. / négative Ref. 18-28-1

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18 1/2”’ | Hand Wind | Swiss Lever | Small Seconds |

Remarks:

Lép. = Lépine = open face movement
Negative winding mechanism
As Ref. 18-28-2 also available as Savonnette (hunter) movement
And with a never negative winding mechanism: references 18-28-1 T (Lépine) and 18-28-2 T (Savonnette)
Cam disk regulator

Listing ID: 11299
Manufacturer / Brand: Zenith
Caliber: 18 1/2''' N.V.S.I. lép. / négative Ref. 18-28-1
Size in French Lignes: 18 1/2''' (40,3 mm)
Size range mm largest diameter: > 40 mm
Shape: Round
Winding: Manual (Crown)
Hands Setting: Crown
Seconds Hand: Small seconds
Escapement: Lever (Swiss, English, Glashütte)
Date, Day, Month...: None
Jewels: 15
Setting Lever Screw/Pin Position: Center
Balance Position: Right (0 - 120°)
Shock Protection: None
Beats per hour: 18,000
Balance Type: Bimetallic screw balance with Breguet hairspring
Power Reserve: Approx. 36 hours
Production Period: 1905 - 1955
Country: Switzerland
Identification: Movement marked with ZENITH. Listed in the Classification Horlgère from 1936 and in the Zenith book from Manfred Rössler. Design already registered in the Swiss Official Gazette of Commerce in 1904.