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_51059 ( "Year" real, "Beer Name" text, "Prize" text, "Category" text, "Competition" text )

### Question ###
What year did maggs magnificent mild win a gold medal in the mild and porter category at the siba south east region beer competition?

### Accurate SQL ###

SELECT AVG("Year") FROM table_51059 WHERE "Beer Name" = 'maggs magnificent mild' AND "Prize" = 'gold medal' AND "Category" = 'mild and porter' AND "Competition" = 'siba south east region beer competition'