The Miyota caliber 8N24 is an automatic skeletonized watch movement made in Japan. It has 21 jewels, beats at 21,600 bph and tells the time via a standard 3 hand display. It is a true no-date movement with only one crown position (time-setting) and no phantom crown position.
The text on a stock rotor of the 8N24 reads: Twenty-One 21 Jewels / Miyota Co. / 8N24 / Japan. You may see the manufacturer’s stock images with the letters CWMJ instead of the caliber number. This abbreviation stands for: Citizen Watch Manufacturing Co. Japan.
Some of the topics covered in this caliber listing:
The caliber 8N24 is available from Miyota in silver or a gold tone gilt color (8N24G). The only difference between these two is the finish. Some brands may choose one over the other depending on the style and colors of the watch the movement will be powering.
Miyota claims that the caliber 8N24 offers accuracy of -20 ~ +40 seconds per day. This is measured within 10-60 minutes from a full wind via the crown. To fully wind the movement, turn the crown 40 times.
Miyota 8N24 VS 8N40:
Miyota also offers a similar skeletonized auto caliber 8N40 with the main difference being that the 8N24 has a central seconds hand and the 8N40 has an offset small seconds subdial at 4:30 on the dial. Both movements use the same 8NXX base framework.
8N24 VS 8N33:
The 8N24 and 8N33 are both 3-hand skeletonized movements from Miyota, however the 8N33 is a manual wind movement and the 8N24 discussed here is an automatic. The 8N33 has 17 jewels whereas the 8N24 has 21. The height of the 8N24 is 1.08mm thicker due to the automatic winding unit: 5.5mm compared to 4.47mm.
8N24 VS 8N26:
There is a similar (and rarely used) Miyota caliber 8N26 with the main difference being that the 8N26 is made for watches with a higher hand position. The taller pinion allows for mounting of hands over a dial (such as the cutout dial featured on the Bulova Futuro). The overall height including the seconds pinion is 6.8mm for the 8N24 and 7.9mm for the 8N26.
Replacement prices for the 8N24 were found online for around $65.00 – $75.95 USD. When ordering wholesale from Miyota, there may be a minimum order quantity of 100 pieces.