Seiko Caliber 6R35

The Seiko caliber 6R35 is an automatic movement that is part of what Seiko refers to as the high performance 6R series caliber. The 6R35 is considered an upgrade from the caliber 6R15. Watches with the 6R35, such as the Presage Arita Porcelain were announced at Baselworld 2019. The Prospex SPB149 powered by the 6R35 was announced in March 2020.

6R15 VS 6R35:

The caliber 6R35 is beginning to find its way into watches that used to house the 6R15. The biggest difference between the two movements is a 20 hour increase in power reserve. The 6R15 has a power reserve of approximately 50 hours and the 6R35 has a power reserve of approximately 70 hours.

6R35 / 6R35A / 6R35B / 6R35C:

This is still a rather new movement, so currently there is only the 6R35A. The general caliber number is 6R35, with 6R35A being the first version. The subsequent letter variations indicate evolution stages in the movements development. This post will be updated if the movement gets any upgrades.

Accuracy of the 6R35:

Seiko claims the accuracy of the caliber 6R35 has a rating of -15/+25 seconds per day in normal temperature conditions (between 5 – 35 degrees C).

Seiko says this about accuracy:

• The accuracy of mechanical watches may not fall within the specified range of time accuracy because of loss/gain changes due to the conditions of use, such as the length of time during which the watch is worn on the wrist, arm movement, whether the mainspring is wound up fully or not, etc.
• The key components in mechanical watches are made of metals which expand or contract depending on temperatures due to metal properties. This exerts an effect on the accuracy of the watches. Mechanical watches tend to lose time at high temperatures while they tend to gain time at low temperatures.
• In order to improve accuracy, it is important to regularly supply energy to the balance that controls the speed of the gears. The driving force of the mainspring that powers mechanical watches varies between when it is fully wound and immediately before it is unwound. As the mainspring unwinds, the force weakens.
• Relatively steady accuracy can be obtained by wearing the watch on the wrist frequently for the self-winding type and winding up the mainspring fully everyday at a fixed time to move it regularly for the wind-up mechanical type.
• When affected by external strong magnetism, a mechanical watch may loss/gain time temporarily. The parts of the watch may become magnetized depending on the extent of the effect. In such a case, consult the retailer from whom the watch was purchased since the watch requires repair, including demagnetizing.

Power Reserve:

The caliber 6R35 holds a power reserve of at least 70 hours. To fully wind the mainspring, turn the crown a minimum of 55 times.

Crown Position Functions:

0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
1 (pulled out one click): Clockwise = Nothing / Counterclockwise = Date setting
2 (pulled out two clicks): Time setting clockwise and counterclockwise

Can you overwind the movement?

No. According to the Seiko documentation, manually winding the movement after it is already fully wound will not break the spring.

When can you adjust the date?

Do not adjust the date between 9:00 PM and 1:00 AM.

Stem Removal:

To remove the stem, make sure the crown is in position 0 or normal position (not date or time setting position). There is a lever with a small indentation for your tool. Gently press down while pulling the stem out. See official instructions below for more guidance:

How often does the 6R35 need serviced?

According to official Seiko documentation, watches with the caliber 6R35 should be serviced every 2-3 years. Learn all about Seiko service intervals here. At the time of this post, the starting cost of getting this movement overhauled by Seiko is $260.00 USD.

Examples of watches with caliber 6R35:

Additional Resources:

• Seiko 6R35 official instruction manual here