The Seiko 4N21-0020 is a watch model based on the 4N21 movement.
Parts List
| 230N21JN01 | crystal - crystal (inorganic) |
| 30MD5NS1 | crown - crown |
| 30MD5NA1 | crown - crown |
| 0G2180B01 | case back gasket - case back gasket |
| MN01A | band - other band |
| MN06A | band - band |
| 10T07ASH | others - hand |
| 10SC27T1 | others - second hand |
| 10SC27T2 | others - second hand |
| 3AA125F3A6S | others - second hand |
| 3AA125F3ANG | others - second hand |
| 09T13AGM | others - minute hand |
| 09T15ASM | others - minute hand |
| 1BA070A1BAA | others - hour hand |
| 1BA070A1BAC | others - hour hand |
| 2BA090A1BAA | others - minute hand |
| 2BA095A1BAC | others - minute hand |
| DZ0040B01 | others - crown and stem gasket |
| 0351156 | others - winding stem |
| 4N21002026 | others - case |
| 4N210030XG19 | others - dial |
| 4N210030XS19 | others - dial |
| 4N2160 | others - machine code |
| 82833050 | others - case ring |
| 4N2100202F | others - case |
| 2BA095A1BAA | others - minute hand |