The Seiko 8420-5640 is a watch model based on the 8420 movement.
Parts List
| ES5N82SN00 | crystal |
| 25M04EZ1 | crown |
| 0G2100N01 | case back gasket - case back gasket |
| MK60A | band - leather band |
| A130BS | others - push pin |
| 05R30CGH | others - hour hand |
| 05R30CGM | others - minute hand |
| DZ0041B01 | others - crown and stem gasket |
Caliber 8420
