The Seiko 4N21-0520 is a watch model based on the 4N21 movement.
Parts List
| 170A17SN02 | crystal |
| 6K30A1SNG0 | crown |
| 0F155BAA3 | case back gasket - case back gasket |
| AC004BAA1 | case back gasket - crown and stem gasket |
| DK16E | band - leather band |
| 3BA075F1BNG | others - second hand |
| 07T47DGH | others - hour hand |
| 07T47DGM | others - minute hand |
| A110BS | others - push pin (for mb) |
| 4N210520 | others - case back |
| 4N2105207H | others - case |
| 4N210980XS14 | others - dial |
| 4N2164 | others - machine code |
| 82840910 | others - case ring |
| 0351155 | others - winding stem |