A few of my one-of-one knowns - assuming Postcards count:
1909 Superior RPPC - Bancroft
1905 RPPC - Cobb
c1943 RPPC - Dandridge
1940s RPPC - Giles
1950 Winston-Salem Team Issue - Weaver
__________________
...
http://imageevent.com/derekgranger
HOF "Earliest" Collection (Ideal - Indiv): 250/346 (72.3%)
1914 T330-2 Piedmont Art Stamps......: 116/119 (97.5%)
1923 V100 Willard's Chocolate............: 180/180 (100%)