The Seiko 4N21-5090 is a watch model based on the 4N21 movement.
Parts List
| SA0A01SN02 | crystal - crystal |
| 30MD5NA1 | crown - crown |
| 30MD5NS1 | crown - crown |
| 0F170BAA3 | case back gasket - case back gasket |
| DK33D | band - band |
| DK54D | band - leather band |
| 3BA075F1BNG | others - second hand |
| 3BA075F1BNS | others - second hand |
| 1BA040A1BAA | others - hour hand |
| 2BA060A1BAA | others - minute hand |
| 06T03DHH | others - hour hand |
| 06T03DHM | others - minute hand |
| 06T03AGM | others - minute hand |
| A120BS | others - push pin (for lb) |
| 4N210360XB14 | others - dial |
| 4N210360XG14 | others - dial |
| 4N210360XS13 | others - dial |
| 4N2150907E | others - case |
| 4N2164 | others - machine code |
| 4N21509075 | others - case |
| 82842630 | others - case ring |
| 4N215090 | others - case back |
| DZ0040B01 | others - crown and stem gasket |
| 0351155 | others - winding stem |
| 06SC11NG | others - second hand |
| 06SC11NS | others - second hand |
| 06T03ASM | others - minute hand |
| 1BA040A1BAC | others - hour hand |
| 2BA060A1BAC | others - minute hand |