Tracy Barber wrote :

It's definitely Ceylon. The Higgins & Gage catalog on letter "C" only
goes to 1974. It looks "close" to an airmail envelope, but I couldn't
find it in there. Maybe there's an Addendum that I overlooked,
upstairs. Will check later.

Value? Not much... no world cruise, for sure.

Tracy Barber

Hi Tracy and Didier,

I found stamps from Sri-Lanka with the same design in the centre,
catalogued by Yvert as "Fiscaux-Postaux" (stamps for common usage as
normal and revenue stamps).
Issued in 1984.
These stamps are catalogued by Scott in the normal section (Sc #
726-727)

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All the best,
Pierre Courtiade

to answer me, please replace my 1st name by my last one