The Seiko 5S21-7A20 is a watch model based on the 5S21 movement.
Parts List
| 310W74JM02 | crystal |
| 310W74JM | crystal |
| 35M82NH1 | crown |
| 0A2600B01 | case back gasket |
| 0A2600B | case back gasket |
| BPZ60E | band - leather band |
| 0351683 | others - winding stem |
| 82803220 | others - case ring |
| 5S217A10XS24 | others - dial |
| 5S217A20 | others - case back |
| 5S217A20WG | others - case |
| 5S219 | others - machine code |
| A180BS | others - push pin |
| 12SC28TB | others - second hand |
| 0Z0060B01 | others - crown and stem gasket |
| 11TA8AGH | others - hour hand |
| 11TA8AGM | others - minute hand |
Caliber 5S21
