The Seiko 4N21-0550 is a watch model based on the 4N21 movement.
Parts List
| 185P13SN02 | crystal |
| 30E37NA1 | crown |
| 0F175BAA5 | case back gasket - case back gasket |
| 0F170BAA1 | case back gasket |
| AC004BAA1 | case back gasket - crown and stem gasket |
| 86571670 | crystal gasket |
| HB69A | band - metal band |
| 07TG6DGH | others - hour hand |
| 07TG6DGM | others - minute hand |
| 07SC35VG | others - second hand |
| 0351155 | others - winding stem |
| 81180249 | others - bracelet fixing pipe |
| 81611019 | others - bracelet fixing pin |
| 82832995 | others - case ring |
| 4N210550 | others - case back |
| 4N2105506Y | others - case |
| 4N211060XS14 | others - dial |
| 4N2164 | others - machine code |
| 82353995 | others - bezel |