Question: What is the railway number of T 4 II class?
SQL: SELECT "Railway number(s)" FROM "2-18843924-4" WHERE "Class" = 'T 4 II';

Question: What year was the B n2t axle arrangement, which has a quantity of 31, manufactured?
SQL: SELECT "Year(s) of manufacture" FROM "2-18843924-4" WHERE "Quantity" = 31.0 AND "Axle arrangement ( UIC )" = 'B n2t';