Answer: In 1989 Vatican City issued a series of 4 postcards displaying illustrations by David Vangelli of sights in Paris, France.

My research was unable to identify any specific reason why the Vatican issued these postcards. I have attached the UFN Bulletin that describes the postcards, but it does not provide a reason why they were issued.
If anyone knows why the Vatican issued the Paris postcards, please let me know.

CLICK HERE to view the UFN Bulletin for
'City of Paris'

CITY OF PARIS ILLUSTRATIONS BY DAVID VANGELLI POSTCARDS

Notre-Dame Cathedral
Eiffel Tower
Basilica of the Sacred Heart as Seen from Montmartre

Archaeological Park of Cluny
P86-P89 (1989)