The congress was in 1999 (Beijing) but i received today an official card with the special cancelation! Crazy isn't it? 10 years later and they still offer this cancelation!
I don't know what i've experience with it - but i think i had to eat those envelopes as a child or my childdreams was full of red/blue stripes.Everytime i open my mailbox and i see such a airmail envelope my hearth bums a bit faster! I just love it!