The so-called Epistle to the Laodiceans is set forth on pages 478-480 of M.R. James's The Apocryphal New Testament (Oxford 1924). James notes that it exists only in Latin and its earliest appearance is in the Codex Fuldensis, which he dates at 546. It also appears in the Codex Dublinensis (8th cent.). James sets out the entire text in English.
Edgar Goodspeed mentions this Epistle on page 110 of his Modern Apocrypha (Beacon Press 1956) because it appears in a volume titled The Lost Books of the Bible. He describes "the spurious Letter from Paul to the Laodiceans": "The Letter to the Laodiceans, an incoherent jumble of scraps from Paul's authentic letters, known only in Latin, not in Greek, does occur in some few Latin manuscripts of the Bible, and in printed German Bibles before Luther. We cannot be sure it is even as old as the fourth century. It was not written until after the contents of the New Testament were fairly settled."
The Epistle consists of twenty verses - each one a verse from a canonical Pauline epistle. James concluded "It is not easy to imagine a more feebly constructed cento of Pauline phrases."
As it only repeats verses found in the canonical New Testament, it adds no new teaching or insight.
Let me bring you up to speed on this one because the OP is a tad bit unclear.
Avery likes to tell all of us - contra every single Latin version scholar alive - that Jerome wrote the Prologue to the Canonical Epistles, which - over a century after Jerome croaked - tells us that the Comma Johanneum should be in the text and promotes a conspiracy theory. Avery, wanting his precious KJV reading to be vindicated, has informed all of us through his stellar research skills (and by "stellar" I mean "nonexistent") that this is in first-person Jerome blah blah blah.
He made this claim on July 15, 2015 on the old CARM board.
So I asked him something he won't answer:
Since "Paul's Epistle to the Laodiceans" is in Fuldensis (which is what he's arguing about) and:
1) It claims Paul as a first-person author
2) Paul himself said he wrote one and this is recorded in Scripture
...why should I reject that claim? Not only is it EXACTLY THE SAME THING he claims for Jerome, it has the imprimatur of Scripture (that Jerome doesn't).
Why does he insist the one is valid but not the other using the same methodology?
This has not answer because it shows his inconsistency on the subject.
He's made clear here he rejects it - which goes to prove his "first person" argument, the fact it's in Fuldensis AND the fact Paul explicitly says it in Scripture...he rejects. But he accepts the other simply because he wants it to be true.
Bear in mind I reject BOTH - because unlike KJVOs, I'm consistent.