Midrash for Bava Metzia 55:16
אמר רב יוסף לא קשיא כאן במקדש ראשון כאן במקדש שני
— But it had a perforation at the side of a certain letter. If he identifies the ribbon [with which the divorce was tied], and she does likewise, it must be given to her. Wherewith [is it identified]? Shall we say, by [its colour], white or red? perhaps she saw it whilst he was holding it! — Hence, by its length. If he states, [it was found] in a valise, and she states likewise, it must be surrendered to him. Why? She knows full well that he places whatever he has [of his documents] in a valise.<span class="x" onmousemove="('comment',' Though this does not prove his ownership either, it must nevertheless be surrendered to him, since she cannot be declared free after a valid doubt has arisen. ');"><sup>14</sup></span>