user: Question: Which SECR numbers have a class of B1?
Columns: ['Class', 'Wheel arrangement', 'LCDR number(s)', 'SECR numbers', 'Manufacturer', 'Year made', 'Quantity made', 'Quantity preserved', 'Year(s) withdrawn']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)', 'William Kirtley (1874–1898)']
SQL:

assistant: SELECT "SECR numbers" FROM "Table" WHERE "Class" = 'B1';