The Seiko 4N21-5370 is a watch model based on the 4N21 movement.
Parts List
| RE4A21SN02 | crystal - crystal |
| 6M35B3SNW0 | crown - crown |
| 6M35B3NNG1 | crown |
| 0F170BA1S | case back gasket - case back gasket |
| D107AG | band - band |
| D107FG | band - band |
| DC44AW | band - band |
| DC45AW | band - band |
| DC46AW | band - band |
| 3BA050F1BNG | others - second hand |
| 1BA030A1BNS | others - hour hand |
| 3BA050F1BNS | others - second hand |
| 1BA030A1BNG | others - hour hand |
| 2BA047A1BNS | others - minute hand |
| 2BA047A1BNG | others - minute hand |
| A100BS | others - push pin (for mb) |
| 4N212310XB13 | others - dial |
| 4N212310XL13 | others - dial |
| 4N212310XS13 | others - dial |
| 4N212310XS23 | others - dial |
| 4N212310XS24 | others - dial |
| 4N2165 | others - machine code |
| DZ0040B01 | others - crown and stem gasket |
| 0351155 | others - winding stem |
| 4N21537079B | others - case |
| 4N21537075A | others - case |
| 82836890 | others - case ring |
| 4N215370 | others - case back |
| 4N21537079A | others - case |