The Seiko 3421-521A is a watch model based on the 3421 movement.
Parts List
| RE2N02GN00 | crystal |
| 30M06NA1 | crown - crown |
| 30M06NS1 | crown - crown |
| 0G0055B01 | case back gasket - crown and stem gasket |
| 0A1900N0 | case back gasket |
Caliber 3421
Seiko 3421-521A Watch Guide