Question: What are the serial numbers for the locomotives of Class 4-8-4 — ooOOOOoo — Northern?
SQL: SELECT "Serial numbers" FROM "2-18620528-14" WHERE "Class" = '4-8-4 — ooOOOOoo — Northern';

Question: What is the fleet number for the model with Serial number 68056?
SQL: SELECT "Fleet number(s)" FROM "2-18620528-14" WHERE "Serial numbers" = '68056';

Question: What is the serial number of the model made in 1930?
SQL: SELECT "Serial numbers" FROM "2-18620528-14" WHERE "Year made" = '1930';

Question: What is the wheel arrangement for the model that was retired in 1955?
SQL: SELECT "Wheel arrangement" FROM "2-18620528-14" WHERE "Year(s) retired" = '1955';