Mainspring for Seiko 6138 and 6139 movements

This is a new Swiss-made replacement mainspring compatible with the vintage Seiko movements listed below. Please note, the mainspring barrel and arbor shown in the listing images are for reference only and are not included. They are simply there to demonstrate how the replacement mainspring fits within the original Seiko mainspring barrel. While the tail of the new generic replacement mainspring doesn't fit as tightly on the arbor as the original Seiko version, it still engages properly with the arbor hook and functions as expected.

Compatible Seiko Movement Numbers:

• 6138A & 6138B
• 6139A & 6139B