The Seiko caliber 6R64 is an automatic GMT movement with a date subdial and power reserve indicator. This caliber is found in the Presage Sharp Edged Series GMT lineup that was announced on February 24, 2021.
In Seiko’s own words:
“Caliber 6R64. Perfect for the international traveler. All four watches are powered by the eight beat-per-second GMT Caliber 6R64. The GMT hand on each is in a different color to stand out clearly from each dial and, like the hands and indexes, has a generous layer of Lumibrite, to ensure legibility. The GMT hand can also be used as a dual time indicator, with the hour hand being adjustable even as the minute and seconds hands continue to mark time. The dial rings are in two colors to separate the night and day hours at a glance. The date is shown on a sub-dial at the six o’clock position and there is a power reserve indicator at nine o’clock.” –source
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6R64 / 6R64A / 6R64B / 6R64C:
The general caliber number is 6R64, with 6R64A being the first version. The subsequent letter variations indicate evolution in the movements development. As of this post, there is only a caliber 6R64A (which is the same as 6R64).
Accuracy of the 6R64:
The Seiko caliber 6R64 is adjusted/regulated at the factory. Seiko officially claims this movement is capable of an average daily rate of +25 to -15 seconds per day in normal temperature conditions (between 5 – 35 degrees C).
Seiko says this about accuracy claims:
“Due to the characteristics of mechanical watches, any actual daily rate may not fall within the range of time accuracy specified above dependent on the conditions of use, such as the length of time during which the watch is worn on the wrist, temperature, arm movement, and whether the mainspring is wound up fully or not, etc.” –source
The caliber 6R64 holds a power reserve of at least 45 hours.
According to Seiko, it only takes five full rotations of the crown to power the watch to run for about 10 hours. The crown winding direction is clockwise, or forwards. Winding backwards or counterclockwise will do nothing. It is recommended that when winding the crown, the rotations are made slowly.
Wearing the 9R65 powered watch for 12 hours/day over the span of 3-5 days will get the movement to full power reserve.
1 (pulled out one click): Clockwise/Counterclockwise = Setting the hours and date
2 (pulled out two clicks): Minutes/GMT hand setting clockwise and counterclockwise (counterclockwise will advance the hands forward)
Can you overwind the movement?
How do you adjust the date?
The date on the 6R64 is set with the hour hand. When the crown is pulled out one click (position 1), you can rotate the crown forwards or backwards to advance the hours, which will change the date when you pass midnight in either direction. It is ok to go clockwise or counterclockwise to set the calendar forwards or backwards. Seiko recommends going in the direction that is nearest to your desired date, presumably so that you put less wear and tear on the gears and setting mechanisms.
To avoid damaging your watch movement, do not adjust the date when the hands are set between 9:00 PM and 3:00 AM.
The 6R64 has a date hand at 6:00 rather than a traditional calendar window. According to Seiko documentation, the date hand should advance between 11:45PM and 12:30AM, while the watch is running normally. This span changes when you are advancing the date manually by turning the crown. In that case, the hand may advance anywhere between 9:00PM and 3:00AM, so do not be alarmed if you see this difference in date flipping.
How often does the 6R64 need serviced?
According to official Seiko documentation, watches with the caliber 6R64 should be overhauled every 2-3 years. Learn all about Seiko service intervals here. At the time of this post, the starting cost of getting this movement services by Seiko is $260.00 USD.
In Seiko’s own words:
“Periodic inspection and adjustment by disassembly and cleaning (overhaul) is recommended approximately once every 3 to 4 years in order to maintain optimal performance of the watch for a long time.” –source (Grand Seiko instruction manual)
Replacement prices for the Seiko 6R64A are not available because the movement is not available for individual sale. If you have an issue with your 6R64 powered watch, you should first consider taking it/sending it in to a Seiko authorized repair center. If you do not want to have Seiko service your timepiece, the only way to get parts for repair may be to purchase a used watch on the secondary market. Retail prices for new Seiko Presage watches with this movement are around $1,400 USD at the time of this post.