CREATE TABLE table_10731 ("Number Range" CLOB, "Introduced" CLOB, "Builder" CLOB, "Engine" CLOB, "Seats" CLOB, "Withdrawn" CLOB)

What date was introduced where it was withdrawn 1955?
SELECT "Introduced" FROM table_10731 WHERE "Withdrawn" = '1955'
SELECT "Introduced" FROM "table_10731" WHERE "Withdrawn" = '1955'