CREATE TABLE table_68770 ("Estimate" CLOB, "Name" CLOB, "Nat." CLOB, "Ship type" CLOB, "Where sunk" CLOB, "Date" CLOB)

Which nation had a battlecruiser with an estimate of 513?
SELECT "Nat." FROM table_68770 WHERE "Ship type" = 'battlecruiser' AND "Estimate" = '513'
SELECT "Nat." FROM "table_68770" WHERE "Estimate" = '513' AND "Ship type" = 'battlecruiser'