user: Question: What is the Diameter of the Dog sled (gold variant) Theme coin?
Columns: ['Year', 'Theme', 'Face Value', 'Weight', 'Diameter', 'Mintage', 'Issue Price']
Types: ['real', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: [2006.0, 'Dog sled', 'Thirty dollars', '31.50 g', '40mm', 15000.0, '$89.95']
SQL:

assistant: SELECT "Diameter" FROM "Table" WHERE "Theme" = 'Dog sled (gold variant)';