The Seiko 3F31-0B20 is a watch model based on the 3F31 movement.
Parts List
| 185W10SV01 | crystal - crystal |
| 30MK8NA4 | crown - crown |
| 0F180NA1S | case back gasket - case back gasket |
| ZB46A | band - metal band |
| 07SC06DG | others - second hand |
| 81606439 | others - bracelet fixing pin |
| 81180229 | others - bracelet fixing pipe |
| 0354735 | others - winding stem |
| 82832280 | others - case ring |
| 3F310B10X914 | others - dial |
| 3F310B20 | others - case back |
| 3F310B20SA | others - case |
| 3F310B20XS14 | others - dial |
| 3F311 | others - machine code |
| 1BB050L0BDG | others - hour hand |
| 1BB050L0BCC | others - hour hand |
| EZ0035B01 | others - crown and stem gasket |
| 2AB075L0BCC | others - minute hand |
| 2AB075L0BDG | others - minute hand |