| Country | Action | Action Date | Effective Date |
|---|---|---|---|
| BELGIUM | Signature | 18/03/1931 | |
| DENMARK | Signature | 18/03/1931 | |
| FINLAND | Signature | 18/03/1931 | |
| GREECE | Signature | 18/03/1931 | |
| ITALY | Signature | 18/03/1931 | |
| LATVIA | Signature | 18/03/1931 | |
| LUXEMBOURG | Signature | 18/03/1931 | |
| NETHERLANDS THE | Signature | 18/03/1931 | |
| NORWAY | Signature | 18/03/1931 | |
| SPAIN | Signature | 18/03/1931 | |
| SWEDEN | Signature | 18/03/1931 | |
| SWITZERLAND | Signature | 18/03/1931 | |
| UNITED KINGDOM | Signature | 18/03/1931 |