The Seiko 4M21-0A20 is a watch model based on the 4M21 movement.
Parts List
| 270WA4SK01 | crystal |
| 8M35C2STWA | crown - crown |
| 0F260NA1S | case back gasket - case back gasket |
| 80607382 | pusher - button |
| DB86AW | band - band |
| D0M4AZ | band - band |
| 1BB080A0BAC | others - hour hand |
| 1BF080L0BCH | others - hour hand |
| 2BB115A0BCC | others - minute hand |
| 2BF115L0BCH | others - minute hand |
| 12ST08CS | others - second hand |
| 81400709 | others - button spring clip |
| EG0060B01 | others - button gasket |
| 4M210A10XS13 | others - dial |
| 4M210A40XS13 | others - dial |
| 4M211 | others - machine code |
| A170BS | others - push pin |
| 0351552 | others - winding stem |
| 82837180 | others - case ring |
| 4M210A2061 | others - case |
| 4M210A20 | others - case back |
| AD006BA12 | others - crown gasket |
Caliber 4M21
Other models with the same movement
| 4M21-0010 |
| 4M21-0A10 |
| 4M21-0A30 |
| 4M21-0A40 |
| 4M21-0A50 |
| 4M21-0A60 |
| 4M21-0A70 |
| 4M21-0A80 |
| 4M21-0A90 |
| 4M21-0B00 |
| 4M21-0B0A |
| 4M21-0B10 |
| 4M21-0B20 |
| 4M21-0B30 |
| 4M21-0B40 |
| 4M21-0B50 |
| 4M21-0B60 |
| 4M21-0B70 |
| 4M21-0B80 |
| 4M21-0B90 |
| 4M21-0C00 |
| 4M21-0C10 |