There are no extant copies prior to that time - NOR any written record from any source prior to that time referring to a pre-Christian Septuagint. Surely, if there was any OT in Greek before Christ, someone would have referred to it or quoted it - yet there is no record of it until Origen - several hundred years afterwards, in a book he put together of various OT translations. Origen attirbutes it to pre-Christian scholars, yet there is only this heretic's and Bible corrector's own words for it - not any outside proof.