The Seiko 4N21-0900 is a watch model based on the 4N21 movement.
Parts List
| 180A02SN02 | crystal - crystal (sapphire) |
| 6M35B1NNG1 | crown |
| 0F150BAA5 | case back gasket - case back gasket |
| D077CG | band - metal band |
| 3BA075F1BNG | others - second hand |
| 2BB072A1BNG | others - minute hand |
| 82832995 | others - case ring |
| 4N210900 | others - case back |
| 4N2109007HA | others - case |
| 4N211800XS14 | others - dial |
| 4N211810XL14 | others - dial |
| 4N2164 | others - machine code |
| B090BS | others - push pin |
| DZ0040B01 | others - crown and stem gasket |
| 0351155 | others - winding stem |
| 1BB050AABNG | others - hour hand |
| 1BB050A1BNG | others - hour hand |
| 2BB070ABBNG | others - minute hand |