The Seiko 4N21-0400 is a watch model based on the 4N21 movement.
Parts List
| 180P15SN02 | crystal |
| 25M25NA4 | crown |
| 0F160BAA5 | case back gasket - case back gasket |
| 0F140BAA3 | case back gasket - case back gasket |
| 86566710 | crystal gasket |
| HK61C | band - leather band |
| 07SC29DG | others - second hand |
| DZ0040B01 | others - crown and stem gasket |
| 0351155 | others - winding stem |
| 82833415 | others - case ring |
| 4N210400 | others - case back |
| 4N2104007XA | others - case |
| 4N210800XS14 | others - dial |
| 4N2164 | others - machine code |
| 82352995 | others - bezel |
| A120AS | others - push pin |
| 07T93JGM | others - minute hand |
| 08TA5JGH | others - hour hand |