Good idea to look up the local press and the stamp oriented press as well. I might try starting with Linn's Stamp News, and perhaps also the Air Post Journal (the American Air Mail Society's magazine).
A couple of other places to inquire might be:
The American Air Mail Society's Pan Am Study Unit at:
J. L. Johnson, Jr. 248 Shore Ave Groton CT 06340-5926 Email: fam14 @tvcconnect.net
and the American Air Mail Society's
Metropolitan Air Post Society c/o Ernest Wheeler 7 Evelyn Terrace Wayne NJ 07470-3446
http://mapsnewyork.org/ Email:ernest wheeler@hotmail.com These guys cover the New York City metropolitan region in membership, though of course their air mail interests span the entire range. I was just thinking that since Interpex 1959 was in their area that they might have some extra knowledge on it.