CREATE TABLE table_346 ("Number Range" TEXT, "Introduced" TEXT, "Builder" TEXT, "Engine" TEXT, "Weight  ( long tons ) " TEXT, "Seats" TEXT, "Withdrawn" TEXT, "Notes" TEXT)

what's the notes where withdrawn is 1956 57
SELECT "Notes" FROM table_346 WHERE "Withdrawn" = '1956–57'
SELECT "Notes" FROM "table_346" WHERE "Withdrawn" = '1956–57'