| Issuer | Date | Desc | State | ||
| - | |
Bulgaria | 6/24/1968 | empty sheet (#5904) | incomplete |
| - | |
Bulgaria | 10/19/1968 | empty sheet (#5903) | incomplete |
| - | |
Bulgaria | 10/19/1968 | empty sheet (#5906) | incomplete |
| - | |
Bulgaria | 11/25/1968 | empty sheet (#5905) | incomplete |