Young Kyu Kim, in his article Palaeographical Dating of p46 to the Later First Century (pdf), which originally appeared in Biblica Magazine, Vol. 69, No. 2, in 1988 (pp. 248-257), wrote that the evidence from the handwriting style and linguistics...
...strongly suggests that p46 was written some time before the reign of the emperor Domitian.Since Domitian reigned from 81 to 96 A.D., if Kim is correct, then latest date when the P-46 manuscript could have been copied down was sometime no later than the vicinity of 81 A.D. Although it appears that most of his fellow scholars have demurred from his date as too early, in my amateur opinion Kim's case seems stronger than his objectors.1
The history of the discovery of the codex has been an adventure of its own. P-46 "was reportedly discovered in 1930 near Fayrum, Egypt,"2 although that provenance cannot be confirmed. The reason it cannot be confirmed, is because value of the individual leaves at the time, if sold separately on the manuscript market, was greater than the price that the whole codex would have fetched. So its unknown discoverer broke it up and sold the pages piecemeal.
Since that time, what are believed to be the surviving 172 pages of the original 208 pages of the codex (which is thought to have included the two books of Timothy and Titus as well as the Church Epistles), have been collected by the Chester Beatty Library in Dublin, which has 112 leaves, and by the University of Michigan, which has 60 leaves.
The book, A Third Century Papyrus Codex of the Epistles of Paul (Ann Arbor, Michigan: 1935), edited by H.A. Sanders, contains facsimiles of the 86 leaves that were in Dublin at the time. But this work is not only out of print, it has been impossible to find on the rare books market, for me anyway. However, it is available for viewing at The Center for the Study of New Testament Manuscripts, and at the The Library of Congress. Plus all of the 112 original leaves now owned are on permanent display at the Chester Beatty Library.
Of the P-46 leaves owned by the University of Michigan, the high resolution images that are available for download on the school's website are, at present, most easily accessed through the links on a post at the blog Evangelical Textual Criticism.
By my back-of-the-napkin calculations (no calculator needed), if Bullinger's estimate in Appendix 180 of The Companion Bible (page 203) is correct -- that the Church Epistles and the epistles to Timothy and Titus were written from 52 to 68 A.D. -- it would mean that this codex is, more or less, only thirteen years newer than the newest autograph, also known as the originals. Which is exciting enough to anyone who is a workman of God's Word, but most especially to those who recognize the significance of the Church Epistles.3