user: Question: Which metal has a size that is 26mm (across scallops)?
Columns: ['Denomination', 'Metal', 'Weight', 'Shape', 'Size']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['One Paisa', 'Aluminium-Magnesium', '0.75 g', 'Square', '17mm (Diagonal)']
SQL:

assistant: SELECT "Metal" FROM "Table" WHERE "Size" = '26mm (across scallops)';