The Seiko 8Y21-5120 is a watch model based on the 8Y21 movement.
Parts List
| RE0A81J20B | crystal |
| 35M37NA1 | crown |
| 35M37NS1 | crown |
| 0F220BAA3 | case back gasket - case back gasket |
| DB0055B01 | case back gasket - crown and stem gasket |
| B1757G | band |
| B1757S | band |
| B1757G-BK5G | clasp - clasp |
| 3AA125F1ANG | others - second hand |
| 0351112 | others - winding stem |
| 82808990 | others - case ring |
| 8Y210330XB14 | others - dial |
| 8Y210330XN14 | others - dial |
| 8Y215120 | others - case back |
| 8Y21512075 | others - case |
| 8Y21512079 | others - case |
| 8Y2183 | others - machine code |
| A140BS | others - push pin |
| 2AF085L0BNG | others - minute hand |
| 09SC31T1 | others - second hand |
| 09P53NGM | others - minute hand |
| 1AF055L0BNG | others - hour hand |
| 09P53NGH | others - hour hand |
Caliber 8Y21
