Is a post period translation of an original text a primary source?
No, the translation is only a primary source for the translation and that is post 1600. Only the original document itself is a primary source. Of course it is doubtful that you will get to use the original document. Therefore, cite that you used a photocopy of the original document if that is the case and the source of that copy. Also if you are using a translation, you might want to identify who did the translation and when.