The Miyota caliber 821A is a self-winding automatic movement in the 82XX family. It has 21 jewels and is made in Japan.
Some of the topics covered in this caliber listing:
There are 3 variants of the caliber 821A from the factory. Everything is the same except for the calendar wheel. The dial on your watch may vary depending on the variation, this will be up to the watch manufacturer and the style of the watch. Please comment below to let us know what you watch model is and where the date is located on the dial.
821A-43A – Date at 3:00, black text on a white background date wheel, square window shape.
821A-43Z – Date at 6:00, black text on a white background date wheel, square or round window shape.
821A-43K – Date at 3:00, white text on a black background date wheel, square window shape.
There is also a gilt version with the same caliber number. The gilt version has a gold tone finish.
821A VS 8215:
The 821A is based on the caliber 8215 which is very popular in the affordable automatic watches category. The main difference between the 821A and 8215 is that the 821A has a decorated finish and a cutout rotor instead of a solid half circle.
In Miyota’s own words, the 821A features:
Fine finishing with barrel bridge
When microbrands use the caliber 8215, they may use a solid caseback or customize the rotor with a sticker or other application. It’s more common to see 821A powered watches with an exhibition caseback as the 821A is considered to be more attractive thanks to the higher level of finishing.
Brands sometimes don’t even realize which version they are using and will sometimes incorrectly label an 821A as an 8215. This has caused some confusion in the community. To be sure, always look at the rotor.
8215/821A rotors/finishing compared:
There is also a caliber 820A with the main difference being that the 820A has a day/date complication, whereas the 821A only has the date option. Interesting note: The 820A is the decorated version of the caliber 8205, which is the day/date version of the 8215.
Accuracy & Power Reserve:
Miyota claims the caliber 821A has an accuracy rating of -20 ~ +40 seconds per day. This is only measured within 10 to 60 minutes from a full power reserve. To achieve full power reserve, hand-wind the crown 40 times. Power reserve or fully wound running time is about 42 hours.
The Miyota 821A is one of the modern automatic movements that experiences a stuttering or hesitating second hand due to the indirect-drive system for running the central seconds. Learn all about it.
Upgraded Hacking Seconds:
As of mid-2019, Miyota seems to have listened to the desires of the watch community and found a way to integrate a hacking mechanism (stop seconds device) into the 821A. This means that the seconds hand will stop when the crown is pulled out. We have reached out to Miyota and will update this listing as soon as we have a reply with more information as to when they made this change. Keep in mind that although there are 821A movements popping up on the market, the current majority of 821A powered watches will be non-hacking. If you watch doesn’t hack, it doesn’t mean it’s broken.
Replacement prices were found online in the $40-50 range for individual movements. Despite the higher level of finishing, the price is not too far from what you can expect when buying an individual caliber 821A. Although the plastic movement holder (part 500-710) is more common in affordable watches, this is interchangeable with a metal ring (502-008).
When ordering wholesale from Miyota, the minimum unit order for the caliber 821A comes in packages of 100 with a lead time of around 2 months.
Miyota 821A Macro Gallery:
The photos are from a Detroit Watch Company “Pride of Detroit” watch.