Question: When the face value is 42¢, what was the issue's date?
SQL: SELECT "Date of issue" FROM "1-15635768-1" WHERE "Face Value" = '42¢';

Question: Which location has the ecosystem of Kelp Forest?
SQL: SELECT "Place of issue" FROM "1-15635768-1" WHERE "Ecosystem" = 'Kelp Forest';

Question: How many stamps have a face value of 37¢ and were printed in the Banknote Corporation of America?
SQL: SELECT COUNT("No. stamps in sheet") FROM "1-15635768-1" WHERE "Face Value" = '37¢' AND "Printer" = 'Banknote Corporation of America';

Question: Who was the printer of Estes Park, Colorado?
SQL: SELECT "Printer" FROM "1-15635768-1" WHERE "Place of issue" = 'Estes Park, Colorado';

Question: The stamp was 39¢, who was the printer?
SQL: SELECT "Printer" FROM "1-15635768-1" WHERE "Face Value" = '39¢';