| Name | Issues/Designs | |||
| Danube Commission | 1856 | — | founding | |
| NATO | 1949 | — | founding (2) - 60th Anniversary of ... / 5th Anniversary of Bulgaria's membership in ..., 50th Anniversary of ... syns. Atlantic Club | |
| Scouting | 1931 | — | founding syns. Scout Movement, Scouting Movement | |
| World Wildlife Fund | 1961 | — | founding |