Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_39 ( nat VARCHAR, ship_type VARCHAR, estimate VARCHAR )

### Question ###
Which nation had a battlecruiser with an estimate of 513?

### Accurate SQL ###

SELECT nat FROM table_name_39 WHERE ship_type = "battlecruiser" AND estimate = "513"