The Seiko 5P31-5B20 is a watch model based on the 5P31 movement.
Parts List
| RE6N36GN00 | crystal |
| 30MA6NA1 | crown - crown |
| 0G0055B01 | case back gasket - crown and stem gasket |
| 0H2600N01 | case back gasket - case back gasket |
| Z1343G | band - metal band |
| Z1344G | band - metal band |
| Z1344G-BK5G | clasp - clasp |
| Z1343G-BK5G | clasp - clasp |
| 08T02NGH | others - hour hand |
| 08T02NGM | others - minute hand |
| 08T10DGH | others - hour hand |
| 5P315B20 | others - case back |
| 5P315B2025 | others - case |
| 5P315B40XG14 | others - dial |
| 5P315B50X984 | others - dial |
| 5P315B50X994 | others - dial |
| 5P319 | others - machine code |
| 82800460 | others - case ring |
| A160BS | others - push pin |
| 0351670 | others - winding stem |
| 08T10DGM | others - minute hand |
| 13SC04A2 | others - second hand |