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_66386 ( "Title" text, "Series" text, "Director" text, "Production Num." text, "Release date" text )

### Question ###
What release date has 6998 as the production num.?

### Accurate SQL ###

SELECT "Release date" FROM table_66386 WHERE "Production Num." = '6998'