Answers by Expert:
United States - Virtually any kind of stamp, cover, essay, proof, cancel, covers, etc.
I have my own expertizing service - Weiss Expertizing. See here;
APS (Life member), USSS, UPSS, USPCS, USCC, EFO Club
Awards and Honors
Too numerous to list here - I have been exhibiting for over 40 years, so have accumulated lots of awards. Also for books I have written.
Thousands different. We ran Public Auctions for 25+ years and I have been a dealer since 1972.