And, now, for something completely philatelic ...
Q/ Are you familiar with an "Air Mail Test" that occurred at the time of Interpex 1959?
Fun fact: That stamp of the India 1958 exhibition in New Delhi is more easily researched than the exhibition itself
India New Delhi Exhibition
Catalog codes:
Stamp Number IN 323
Stanley Gibbons IN 421
Yvert et Tellier IN 106
Michel IN 303
Issued on: 1958-12-30
Perforation: comb 14½ x 14
Printing: Photogravure
Colors: Dark lilac
Face value: 15 Indian naye paisa
Print run: 11,916,340
... a photo of PM (Prime Minister! not Private Message!) Nehru visiting the India 1958 exhibition
Q/ Any other "Air Mail Test" covers & cards out there?
Cheers,
/s/ ikeyPikey
Edited to append: Postcard from the collection of Michael Lebbert.