The Seiko 4N21-5520 is a watch model based on the 4N21 movement.
Parts List
| RE3A59S20A | crystal - crystal (sapphire) |
| 27M19DE1 | crown |
| 0H1800B01 | case back gasket - case back gasket |
| XX000 | band - band |
| 1CC035A1BNG | others - hour hand |
| 2CC057A1BDG | others - minute hand |
| A130AS | others - push pin (for lb) |
| 4N201860XA14 | others - dial |
| 4N2164 | others - machine code |
| DZ0040B01 | others - crown and stem gasket |
| 4N20552043A | others - case |
| 82834070 | others - case ring |
| 4N205520 | others - case back |
| 0351155 | others - winding stem |