The Seiko 4N00-6421 is a watch model based on the 4N00 movement.
Parts List
| ES3A49J20C | crystal - crystal |
| ES3A49J20B | crystal - crystal |
| ES3A49J20A | crystal - crystal |
| 6M30B9NNG1 | crown - crown |
| 6M30B9NN | crown |
| 0H1400B01 | case back gasket - case back gasket |
| 0H1400B0 | case back gasket |
| 4279LZ | band - band |
| 4279KZ | band - band |
| 4279KZ-LKG | band - link |
| 4279LZ-LKG | band - link |
| 4279LZ-BK4G | clasp - buckle |
| 4279LZ-PB1 | clasp - parts for buckle |
| 4279KZ-BK4G | clasp - buckle |
| 4279KZ-PB1 | clasp - parts for buckle |
| 4N00642125B | others - case |
| 4N00642125C | others - case |
| 4N0064212HA | others - case |
| DZ0040B01 | others - crown and stem gasket |
| 4N004271XB14 | others - dial |
| 4N004271XG14 | others - dial |
| 4N004271XS14 | others - dial |
| 4N004271XS24 | others - dial |
| 4N0061 | others - machine code |
| 81190075 | others - bracelet fixing pipe |
| 81606899 | others - bracelet fixing pin |
| 82870930 | others - case ring |
| 4N00642125A | others - case |
| 4N006421 | others - case back |
| 0351550 | others - winding stem |
| 0351155 | others - winding stem |
| 1CC032A2BNG | others - hour hand |
| 2CC047A2BNG | others - minute hand |