When was the ship that had a fate of 'converted to laker, 1961; still in service' commissioned?
CREATE TABLE "ships_of_the_class" (
  "name" text,
  "original_name" text,
  "commissioned" text,
  "final_decommission" text,
  "fate" text
);
SELECT "commissioned" FROM "ships_of_the_class" WHERE "fate"='converted to laker, 1961; still in service';