American Stamp Dealers Association www.americanstampdealer.com |
American Philatelic Society www.stamps.org |
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U.S. Philatelic Classics Society www.uspcs.org |
The Collectors Club of N.Y. www.collectorsclub.org |
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The Royal Philatelic Society London www.rpsl.org.uk |
Philatelic Traders Society www.thepts.net |
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Philatelic Foundation www.philatelicfoundation.org |
Professional Stamp Experts www.gradingmatters.com |
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P.S.A.G. www.stampauthentication.com |
Professional Coin Grading Service www.pcgs.org |