I think different posts are being conflated, but I think I’m asking the same question you are: Is every ancient translation ‘Septuagint’ or was there one Septuagint translated by the seventy elders? Who decides?
In Orthodox tradition, the Righteous Simeon was one of the Seventy Elders, and he translated the book of Isaiah!!!!
http://orthodoxwiki.org/Simeon_the_God-receiver