The Seiko 4M21-0B50 is a watch model based on the 4M21 movement.
Parts List
| 270WB6SN01 | crystal - crystal |
| 8K40B0SNW1 | crown - crown |
| 0F260NAAS | case back gasket - case back gasket |
| 80607967 | pusher - button |
| EC0060B01 | pusher - pusher gasket |
| D0W1DG | band - band |
| 1BB075A4BAN | others - hour hand |
| 1BC080A1BNG | others - hour hand |
| 2BB115A4BCN | others - minute hand |
| 2BC115A1BNG | others - minute hand |
| 3AA125F0ANB | others - second hand |
| 3AA125F0ANG | others - second hand |
| A100BS | others - push pin (for mb) |
| 4M210B80XS14 | others - dial |
| 4M210C00XS24 | others - dial |
| 4M211 | others - machine code |
| 81401009 | others - washer |
| 0351552 | others - winding stem |
| 81400709 | others - button spring clip |
| 81350540 | others - button spring |
| 82837180 | others - case ring |
| 4M210B50U3 | others - case |
| 4M210B50 | others - case back |
| 0Z0060B01 | others - crown and stem gasket |
Caliber 4M21
Other models with the same movement
| 4M21-0010 |
| 4M21-0A10 |
| 4M21-0A20 |
| 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 |
| 4M21-0B60 |
| 4M21-0B70 |
| 4M21-0B80 |
| 4M21-0B90 |
| 4M21-0C00 |
| 4M21-0C10 |