The Seiko 4N21-0420 is a watch model based on the 4N21 movement.
Parts List
| 170P17SN03 | crystal - crystal |
| 6K30A1SNG0 | crown |
| 0F155BAA3 | case back gasket - case back gasket |
| AC004BAA1 | case back gasket - crown and stem gasket |
| 86561171 | crystal gasket |
| ZA38A | band - metal band |
| 3BA075F1BNG | others - second hand |
| 2BB072A1BNG | others - minute hand |
| A110BS | others - push pin (for mb) |
| 4N210420 | others - case back |
| 4N2104207H | others - case |
| 4N210850XL14 | others - dial |
| 4N2164 | others - machine code |
| 0351155 | others - winding stem |
| 82840910 | others - case ring |
| 1BB050A1BNG | others - hour hand |