Seiko 5106A, 5126A, 5139A mainspring

Genuine Generale Ressorts Swiss-made replacement mainspring for vintage Seiko 5106A, 5126A and 5139A automatic movements.

These calibers belong to Seiko’s vintage 51-series automatic family and can be found in collectible Seiko watches from an important period in the company’s mechanical-watch history.

When servicing a vintage Seiko movement, mainspring quality and dimensional consistency matter. There’s no mystery about what you’re installing: GR2379X is a branded Swiss mainspring made by Generale Ressorts, a leading specialist manufacturer of watch mainsprings.

Is GR2379X compatible with the Seiko 5106A, 5126A and 5139A?

Yes. GR2379X is listed as a replacement automatic mainspring for Seiko/Hattori calibers 5106A, 5126A and 5139A. Because vintage movements may have undergone previous repairs or parts substitutions, compare the existing mainspring and barrel configuration before installation.

Compatible Seiko Movements

5106A
5126A
5139A

Specifications

Manufacturer: Generale Ressorts
Manufacturer Part Number: GR2379X
Type: Automatic mainspring
Height: 0.95 mm
Thickness: 0.125 mm
Length: 380 mm
Barrel Diameter: 10.5 mm

Amplitude Watch Parts ships from the USA, so there’s no need to worry about long overseas shipping delays or tariffs.