CREATE TABLE table_51059 ("Year" FLOAT, "Beer Name" TEXT, "Prize" TEXT, "Category" TEXT, "Competition" TEXT)

What year did maggs magnificent mild win a gold medal in the mild and porter category at the siba south east region beer competition?
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'
SELECT AVG("Year") FROM "table_51059" WHERE "Beer Name" = 'maggs magnificent mild' AND "Category" = 'mild and porter' AND "Competition" = 'siba south east region beer competition' AND "Prize" = 'gold medal'