The Seiko W620-4020 is a watch model based on the W620 movement.
Parts List
| 0F300BAA1 | case back gasket - case back gasket |
| 80632630 | pusher - button |
| 80632459 | pusher - button |
| FBW8HB | band - band |
| FBW9HB | band - band |
| FC49HB | band - band |
| W6204020N2A | others - case |
| W6204020N2B | others - case |
| 81518099 | others - case back screw |
| 81351639 | others - button spring |
| T180CS | others - push pin |
| AD006BA11 | others - crown and stem gasket |
| W6204020N2C | others - case |
| 81334179 | others - button spring (front) |
| 83200211 | others - button spring clip |