The Seiko 5Y31-8A20 is a watch model based on the 5Y31 movement.
Parts List
| 290A03JN02 | crystal - crystal |
| 290A03JN | crystal |
| 290W91JN01 | crystal |
| 290W91JN | crystal |
| 35MJ5NN1 | crown - crown |
| 35MM5NN5 | crown |
| 35MM5NN6 | crown |
| 35MM5NN7 | crown |
| 0F240BAA3 | case back gasket - case back gasket |
| 0F240BAA | case back gasket |
| BPK10G | band |
| BPA90G | band - leather band |
| BPK16G | band - leather band |
| BPK17G | band - leather band |
| BPS03G | band - leather band |
| BPZ62G | band - leather band |
| BPK12G | band |
| BPK11G | band |
| 11T47AGH | others - hour hand |
| 3AA125F1ANG | others - second hand |
| 12SC39T1 | others - second hand |
| 3AA125F3ANG | others - second hand |
| 11T05NGH | others - hour hand |
| 11T05DGM | others - minute hand |
| 1BA080A1BAA | others - hour hand |
| 1BC080A1BNG | others - hour hand |
| 2BC110A1BDG | others - minute hand |
| 0D005BA13 | others - crown and stem gasket |
| EB0055B01 | others - crown and stem gasket |
| 0351671 | others - winding stem |
| 5Y3161 | others - machine code |
| 5Y318A20 | others - case back |
| 5Y318A2075 | others - case |
| 5Y318B60XB14 | others - dial |
| 5Y318B60XS14 | others - dial |
| 5Y318B60XS24 | others - dial |
| 5Y318B70X919 | others - dial |
| 5Y318B70XS19 | others - dial |
| 5Y318B70XS29 | others - dial |
| 82833770 | others - case ring |
| A180BS | others - push pin |
| 10T09DGH | others - hour hand |
| 3AA125F3AN2 | others - second hand |
| 12SC23TG | others - second hand |
| 10T09DGM | others - minute hand |
| 12SC23T1 | others - second hand |
| 2BC110A1BCA | others - minute hand |
| 11SC17T1 | others - second hand |
| 11T05CGM | others - minute hand |
| 2BA120A1BAA | others - minute hand |
| 12T15AGM | others - minute hand |
| 12T07A1M | others - minute hand |
| 12T15AGH | others - hour hand |
| 1BH080A1BAA | others - hour hand |
| 12T35DGM | others - minute hand |
| 2BH115A1BAA | others - minute hand |
| 12T07A1H | others - hour hand |
| 11T77AGM | others - minute hand |
| 12T35DGH | others - hour hand |
| 11T77AGH | others - hour hand |