The Seiko 6R35 is an automatic movement found in various Seiko Prospex and Presage watches. It is an upgraded version of the 6R15 with an improved power reserve.
It features 24 jewels, a 70-hour power reserve, and accuracy rated at -15/+25 seconds per day.
Seiko 6R35 Specifications
| Manufacturer | Seiko |
| Caliber | 6R35, 6R35A |
| Movement Type | Automatic |
| Diameter | 27.40 mm |
| Casing Diameter | 27 mm |
| Height | 5.25 mm |
| Jewels | 24 |
| Hacking | Yes |
| Hand-Winding | Yes |
| Vibrations Per Hour | 21,600 BPH |
| Shock System | Diashock |
| Regulator | ETACHRON |
| Power reserve | Around 70 hours |
| Magnetic resistance | 4,800 A/m (60 gauss) |
| Winding direction | Bi-directional |
| Country of manufacture | Japan |
| Known Watches | Seiko Presage, Seiko Prospex |
Seiko 6R35 Accuracy
The accuracy of the Seiko 6R35 is rated to -15/+25 seconds per day.
Unlike many other Seiko movements, however, users find their watches that use the 6R35 tend to have accuracy on the outer bounds or even slightly outside its specified range.
My SPB197, which uses the 6R35, runs at a not-so-impressive -10 seconds per day. While not awful, I would expect a bit better considering it was a $700+ watch.
Common 6R35 Problems
Users have reported wildly varying accuracies with the 6R35.
Further, the 6R35 can not easily be regulated to improve its accuracy. The 6R35 has been noted to be particularly fragile and difficult to regulate. Unless you’re a very seasoned watch tinkerer, it’s best to take this to a professional.
Watch the video below to learn how to regulate the 6R35 movement, as demonstrated on an SPB143.
Setting the Date
Here is how to set the date on the Seiko 6R35 according to Seiko’s user manual.
1. Pull out the crown with the first click. If the watch has a screw-down crown, first unscrew it.
2. Turn the crown counterclockwise to change the date. Set it to the date prior to the current date.
Follow the next section “setting the time” to complete the process.
Warning: Do NOT set the date between 9:00 p.m. and 1 a.m. Doing so may damage the date-change function. To avoid doing so, set the time to 6:30 AM or PM first. This is well away from the ‘danger zone’.
Setting the Time
1. Pull the crown out to the second click. Doing so will stop the watch’s second hand.
2. You can now set the time by rotating the crown clockwise until the date shifts to the current date. If setting the time to A.M., rotate the crown to the desired time. If you set the time to P.M., rotate the crown forward 12 hours and then to the correct time.
3. Push the crown back in. The second hand will resume its motion. If you have a screw-down crown, you can now screw it back into the case.
Need more help? Watching the short video below for step-by-step instructions.
Winding the 6R35
The 6R35 allows you to hand-wind your watch. That means you can rotate the crown to power the movement. You do not need to worry about over-winding; this is not possible with the design of the movement.
Simply unscrew the crown and rotate it 10-20 full rotations before wearing it on your wrist to kick-start it. Or, wind it 40-50 full rotations to fully power it. With a power reserve of around 70 hours, the 6R35 should be fairly easy to keep powered up with regular winding or frequent wear.
Servicing the 6R35
Seiko suggests you service the 6R35 movement every 2-3 years. If the 6R35 is anywhere near as durable as Seiko’s other movements, however, it won’t be necessary to service the movement more frequently than every 7-8 years, or until you have a specific problem with the movement that requires repair.
A service of any of the 6R calibers, including the 6R35 will cost $260 if sent to Seiko. Independent watchmakers may charge more or less for a service.
Seiko 4R35 vs. 6R35
The 4R35 and the 6R35 are pretty similar, date-only movements. But, the 4R caliber series is used primarily in entry-level watches, while the 6R is used in Seiko’s mid-tier watches, including some of their professional Prospex lineup.
One key difference is the accuracy rating between the 4R and 6R series. The 4R35 movement is rated at -35/+45 seconds. That is significantly less accurate than the -15/+25 seconds for the 6R35.
Another difference is the power reserve, which is 40 hours for the 4R35, and 70 hours for the 6R35.
Watch the video below for a detailed comparison between these two movements.
Seiko 6R15 vs. 6R35
The 6R35 is essentially the upgraded version of the now-discontinued 6R15.
The 6R15 has a power reserve of just 50 hours, while the 6R35 has a power reserve of 70. This means the 6R35 can almost run for an additional day when both are fully wound.
Aside from that, there is no major difference between them. Nonetheless, the 6R35 is in watches that are generally more expensive than the 6R15, likely a result of Seiko simply raising their prices across the board since the 6R15 was much more heavily utilized.
Seiko 6R35A vs. 6R35B vs. 6R35C
As of right now, Seiko only manufactures the 6R35A. If the company upgrades the 6R35 in the future without designating a new caliber number, subsequent versions will be called 6R35B and 6R35C.
Seiko 6R35 vs. ETA 2824
Naturally, you are going to be wondering how the Seiko 6R35 compares to the ETA 2824, one of the most popular Swiss workhorse movements.
The 6R35 has a much higher power reserve than the ETA 2824’s 38 hours. Nevertheless, many watch aficionados will argue that the ETA 2824 is the superior movement given its overall quality and reliability.
It is also worth pointing out that the now-discontinued 6R15 was a great budget alternative to the ETA 2824. But, since watches with the 6R35 cost nearly as much, if not more, than watches that use the ETA 2824, it is not the value proposition that the 6R15 once was.
Watches That Use the Seiko 6R35 Movement
Presage
Seiko has been selling mid-range and premium Presage watches since 2016. The 4R series powers the Basic Line, but some of the watches in the Presage Prestige line feature the 6R35 movement (others feature the 6R15 or the 6L35).
Prospex Alpinist
Seiko launched its Alpinist watches in 1959. As the name indicates, they are aimed at climbers and other outdoor enthusiasts. Modern Alpinist watches, such as the SPB lineup released in 2020, utilize the 6R35.
Prospex Sumo
The 6R35 movement also powers the Prospex Sumo, which is one of Seiko’s professionally rated dive watches.
Prospex SPB143
The SPB143 is a faithful re-edition of their first-ever dive watch, the 62mas. The SPB143 is one of the most expensive Seiko watches to utilize the 6R35 caliber. Although the watch itself is great, many argue that Seiko should have used an upgraded caliber for a watch that costs around $1,000.
Seiko 6R35 Manual
For more information on the 6R35, visit the official user manual here.
Seiko 6R35 Price
Watches containing the Seiko 6R35 often sell for $750 and up. For comparison, watches with the 6R15 generally cost between $300 – $600. Although the 6R35 movement isn’t currently for sale, the comparable 6R15 generally sells for under $300.
Where to Buy Replacement 6R35 Movements
Replacement 6R35 movements aren’t currently available for sale.
Instead, you can use a replacement 6R15, which is not much of a downgrade—you’ll have a lower power reserve of 50 hours instead of 70. However, they can be quite pricey, up to $300!
Instead, you can opt for the much more affordable NE15 or NH35, both of which are compatible with watch cases that use the 6R35.
Summary
The Seiko 6R35 is a mid-tier automatic movement that is an upgrade to the 6R15, increasing the power reserve to 70 hours total.
The movement has 24 jewels, a 70-hour power reserve, and an accuracy rating of -15/+25 seconds per day.
The 6R35 is used in many Presage and Prospex watches, and the movement is a strong competitor to entry-level Swiss movements such as the ETA 2824.
While this movement sometimes suffers from some accuracy problems, on the whole, it is well-designed. It includes valuable complications like hacking and hand-winding, plus an impressive power reserve that can run for almost three full days when fully wound.
The Seiko 6R35 caliber is in the Baby Alpinist I bought for 530 euros and, like all of their mechanical movements, is mass-produced crap, showing wild deviations from minus 30 to plus 60 seconds per 24h observed over 18 months of use and depending on a whole catalog of factors like position, how often worn, degree of winding, temperature etc etc. Their favourite 4R35 is even worse. That doesn’t stop them from using the 6R35 in pieces costing up to almost $2000. Seiko appears to have no interest in precise calibers in their mechanical watches, otherwise they would be able to produce a COSC-certified chronometer for around $1200. Instead they want you to buy their fancy “limited editions” or fork out $thousands for a Grand Seiko.