Seiko Caliber 6R5J Watch Movement

Manufacturer	Seiko
Caliber Number	6R5J, 6R5JA
Base Caliber	Seiko 6R55
Movement Type	Automatic, self-winding mechanical
In-House?	Yes
Diameter	(needs confirmed)
Height	(needs confirmed)
Jewels	24
Beat Rate	21,600 vph
Lift Angle	53 degrees
Power Reserve	~72 hours (3 days)
Rotor Style	Ball-bearing
Hand-Windable?	Yes
Anti-Shock Device	Diashock
Hand Count	4
Functions	Central hours; central minutes; central sweeping seconds; 24 hour indicator subdial at 6:00; skeletonized/open balance wheel at 9:00
Hacking Seconds?	Yes
Finishing	Gold tone rotor
Country of Manufacture	Japan
Known Models	Seiko Presage Sharp Edged Series (Refs: SPB415 aka SARJ001 – White/Shironeri; SPB417 aka SARJ003 – Blue/Aitetsu; SARJ005 – Japan only “Azabu Tailor” model in black and gold) (Add your watch to the comments below…)

The Seiko caliber 6R5J is an automatic movement with an open balance wheel (aka open escapement aka open heart movement as Seiko calls it) and a 24 hour indicator. This caliber is found in the Presage Sharp Edge series which was announced in April 2023 with availability slated for Summer 2023.

In Seiko’s own words:

“A new 6R series movement debuts with the latest Sharp Edged Series watches. With the new Caliber 6R5J, the latest creations boast an increased power reserve of three days when fully wound. The 21,600 vph automatic movement has indications for the hour, the minute, and the seconds, as well as a sub-dial for 24-hour indication at the 6 o’clock position. An eye-catching cutout at the 9 o’clock position shows the signature asanoha, or “hemp-leaf” pattern, which matches the same pattern seen on the dial surface. The movement’s escapement can be viewed and enjoyed through this opening. In recognition of the upgraded 72-hour power reserve, each watch’s dial reads “Automatic 3 Days.” The full expanse of Caliber 6R5J, including its gold-colored oscillating weight, is also visible through an exhibition case back.” –Source

Some of the topics covered in this caliber listing:

Time Setting:

The 6R5J only has one crown position: simply pull the crown out one click for time setting mode.

24 Hour Hand:

The 24 hour hand in the subdial at 6:00 cannot be adjusted independently. It is a day/night or 24 hour indicator, and does not act as a second time zone. The 24 hour hand moves with the main time.

Accuracy:

Seiko claims that the average accuracy of the cal. 6R5J is within -15 to +25 seconds per day at normal operating temperatures in the range of 5C to 35C (41F to 95F).

6R5J VS 6R55:

This comparison is being made because the 6R5J and 6R55 share the same manual and specs table. Everything is the identical between them, except that the 6R55 is a 3-hander with a date at 3:00 (no open balance and no 24 hand). Despite the big difference in functionality, the jewel count and other specs are the same.