| Issuer | Date | Desc | State | ||
| - | |
Bulgaria | 2/24/1998 | empty sheet (#6285) | incomplete |
| - | |
Bulgaria | 6/10/1998 | empty sheet (#6287) | incomplete |
| - | no image | Bulgaria | 6/23/1998 | empty sheet (#6286) | incomplete |
| - | |
Bulgaria | 7/14/1998 | empty sheet (#6288) | incomplete |