Recent celestial activity -- a meteorite that paid a damaging visit to Russia and the near miss of an asteroid -- will naturally draw attention to space philately. Current events are one of the prime engines driving interest in related stamps.
One of the greatest producers of philatelic items relating to space is the Calle family, who have produced both stamps and cachets relating to the subject. Perhaps the best known of their designs is the Man on the Moon stamp, created by the recently departed Paul Calle. His son, Chris has carried on the tradition and has become a prodigious producer of stamp art as well as cachets for space covers and others.
Currently the Connecticut Cover Club (Chapter 85 of the American First Day Cover Society) is offering one of their annual Hall of Fame Covers, which features the moon stamp and franks a cover honoring Paul, featuring a cachet by Chris. It is a great memorial for a great artist who has contributed so much to philately.
To acquire one of these covers for your collection send $3 and a self addressed stamped envelope (#10 size) to Connecticut Cover Club, c/o Arnold A. Agnoli, 70 Old Town Road - Apt. 338, Vernon Rockville, CT 06066.
While you're at it, request a pricelist for other available covers from the club.
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