This manuscript is important for a number of reasons. First, the papyrus was likely written in the 3rd century B.C.E., a period in which our evidence is dominated by the Zenon papyri. Second, the papyrus is of an official nature, probably a formal petition. It mentions petitions, travel, and, interestingly, some antigrapheis that are sent away for some purpose. Third, the papyrus is likely part of the dossier on Zenon, on account of the fact that 1) names common to the Zenon papyri occur here, 2) the acquisition data match the acquisition data of other Zenon papyri at Columbia, and 3) our text is surrounded in H.I. Bell's distribution list by batches of Zenon papyri, which suggests there is a link between the texts in question. These considerations raise the probability (but do not establish absolute certainty) that P.Col. inv. 257 is part of the Zenon dossier, and that for unknown reasons the papyrus has been overlooked thus far.
Another very interesting feature of the papyrus is the occurrence of a previously unattested Greek word. Here is a photograph of the word followed by my commentary in the edition:
I checked all the papyrological literature and this word is nowhere to be found. The fine editors of ZPE also confirmed that it is indeed a new Greek word. I have suggested a possible meaning based on linguistic derivation but I would like to invite readers to offer suggestions here. What are all the possibilities? The full transcript of this line is: [..]αγγέλλεϲθαι ἐπεργείαϲ.