user: Question: What is Type, when Works Number is "unknown"?
Columns: ['Name', 'Builder', 'Type', 'Works Number', 'Built']
Types: ['text', 'text', 'text', 'text', 'real']
Sample row: ['Pioneer', 'Andrew Barclay & Co', '0-4-0 WT (converted to 0-4-2 WT)', 'unknown', 1876.0]
SQL:

assistant: SELECT "Type" FROM "Table" WHERE "Works Number" = 'unknown';