Meeting of 13.7.22 (Official Bulletin 2)
| Country | Prefix | |
|---|---|---|
| Switzerland | C-H | |
| Netherlands | H-N | |
| Spain | M- |
Meeting of 25.10.22 (Official Bulletin 3)
| Country | Prefix | |
|---|---|---|
| Latvia (Lettonia) | B-L | |
| Luxembourg | L-U |
Meeting of 28.2.23 (Official Bulletin 4)
| Country | Prefix | |
|---|---|---|
| Hungary | H-H | |
| Monaco | M-M | |
| Denmark | T-D |
The schedule produced after this meeting also amended a number of marks.
These subsequently reverted to their former marks after the next meeting.
It is not clear whether these were simply typographical errors. The changes were:
| Country | Prefix | |
|---|---|---|
| Uruguay | From C-U to C-M | |
| Ecuador | From E-E to E-U | |
| Haiti | From H-H to H-E |
Meeting of 26.6.23 (Official Bulletin 5)
| Country | Prefix | |
|---|---|---|
| Albania | B-A | |
| Bulgaria | B-B | |
| Costa Rica | K-C | |
| Sweden | S-A |
At this meeting Monaco (M-M) changed to M-O and Hungary was amended to H-M.
Uruguay, Ecuador and Haiti reverted to C-U, E-E and H-H respectively
Meeting of 3.3.24 (Official Bulletin 6)
| Country | Prefix | |
|---|---|---|
| Estonia | E-A | |
| Finland | K-S | |
| Lithuania | Z-L |
Meeting of 14.10.24 (Official Bulletin 7)
| Country | Prefix | |
|---|---|---|
| Argentina | R-A |
Meeting of 6.4.25 (Official Bulletin 8)
| Country | Prefix | |
|---|---|---|
| Chile | B-C |
Meeting of 6.10.25 (Official Bulletin 9)
| Country | Prefix | |
|---|---|---|
| Abyssinia | A-B | |
| Persia | P-I | |
| Free City of Danzig | Y-M |
Meeting of 3.11.26 (Official Bulletin 11)
| Country | Prefix | |
|---|---|---|
| Salvador | Y-S |
Meeting of 25.4.27 (Official Bulletin 12)
| Country | Prefix | |
|---|---|---|
| Afghanistan | Y-A | |
| Dominica | Z-D |
Using a group of 4 letters out of the 26 of the alphabet
Each group containing at least one vowel eg: ADCJ PURN. The letter 'Y' is considered to be a vowel