The Seiko caliber 8T68 (actually marked 8T68A) is found in some Seiko branded watches. This mechaquartz chronograph movement is made in Japan and has zero (0) jewels. This movement has been produced by Seiko since at least 2015.
Some of the topics covered in the caliber listing:
8T68, 8T68A, 8T68B, etc:
8T68 is the base caliber number. The trailing letter is the version. 8T68A is the first version, therefore, 8T68 and 8T68A are the same. If there are any future updates to this caliber, the letter will change to 8T68B and so on.
Seiko 8T68 VS 8T63:
There is a similar caliber 8T63 that shares the same functionality as the 8T68. When comparing these two movements, the main difference between them is that the 8T68 shown here has the subdials at 2:00, 6:00, and 10:00. The 8T63 places the subdials at 3:00, 6:00, and 9:00. Both calibers offer a date feature between 4:00 and 5:00.
The 8T68 has a central stopwatch chronograph hand and a 60 minute totalizer at 10:00. The chronograph is only capable of counting up to 60 minutes in one second intervals. It automatically stops after reaching 60 minutes.
Operating the chronograph is similar to many chronograph watches:
Button A (top button) – Start
Button A (top button) – Stop
Button B (bottom button) – Reset
Resetting the Chronograph Hand to Zero:
The Seiko 8T68 is a mechaquartz movement, so the recalibration is not the same as a regular quartz chronograph since the hands are actually mechanically driven. This is one of the drawbacks of a meca-quartz movement, and if the hands are dramatically misaligned, you may need to have your watchmaker pull them off and install them again in the correct position.
After a battery change, you can try the following instructions for lining up the hands (needs confirmed):
When the small seconds hand on the 6:00 subdial reaches 12:00, pull the crown out to position 2 (2 clicks to time-setting mode).
Press the bottom pusher (button B) for 2+ seconds until the central chronograph hand turns around the dial.
Press the crown back in.
For chronograph troubleshooting, see the following:
In the manual, Seiko claims that a new battery installed in the caliber 8T68 should last approximately 3 years. Keep in mind that the battery will drain faster if you leave the chronograph second hand running – specifically if the chronograph is used for more than 1 hour per day.
There is also a low battery indicator which will cause the small second hand to jump every 2 seconds. The time on your watch will maintain accuracy even in low battery mode.
After replacing the battery, you will need to perform an AC reset. After an AC reset, the second hand may skip 2 seconds for the first 10 seconds.
The original battery in the watch was also made in Japan by Seiko. The size is SR936SW which should convert to a 394 cell.
Seiko claims that the caliber 8T68 will maintain accuracy of +/- 15 seconds per month at normal operating temperatures about 41F to 95F while on the wrist.
At the time of this post, replacement prices of the 8T68 were found online in the range of $27.50 to 43.00 USD.
In Seiko’s Own Words:
“Cal. 8T63A [8T68A] has a new structure employing one crown and two buttons. The construction of chronograph mechanism is based on Cal. 8R28 mechanical chronograph watch by using the one-piece 3 pointed reset hammer. While other Swiss-made watches are using separate hammers which require an assembly and adjustment of the hammers, the one-piece hammer design realizes maximum durability and stability of the component and easier maintenance. It is also equipped with the self-alignment function for all counting hands to return to zero positions instantaneously.” –source