As a box code, 1688 is used for 7 post office box locations.
PO Boxes using 1688
| Suburb | Town | Province |
|---|---|---|
| Rabie Ridge Ext 1 | Rabie Ridge | Gauteng |
| Rabie Ridge Ext 2 | Rabie Ridge | Gauteng |
| Rabie Ridge Ext 20 | Rabie Ridge | Gauteng |
| Rabie Ridge Ext 3 | Rabie Ridge | Gauteng |
| Rabie Ridge Ext 4 | Rabie Ridge | Gauteng |
| Rabie Ridge Ext 5 | Rabie Ridge | Gauteng |
| Rabie Ridge | Tembisa | Gauteng |