| Country | Action | Action Date | Effective Date |
|---|---|---|---|
| BELGIUM | Signature | 29/10/1956 | |
| FRANCE | Signature | 29/10/1956 | |
| ITALY | Signature | 29/10/1956 | |
| MOROCCO | Signature | 29/10/1956 | |
| NETHERLANDS THE | Signature | 29/10/1956 | |
| PORTUGAL | Signature | 29/10/1956 | |
| SPAIN | Signature | 29/10/1956 | |
| SWEDEN | Accession | 05/12/1956 | |
| UNITED KINGDOM | Signature | 29/10/1956 | |
| UNITED STATES OF AMERICA | Signature | 29/10/1956 |