Hermas info was put on a blog, now moved here:
The Shepherd of Hermas, tr. with an intr. and notes by C.H. Hoole (1870)
edited by Charles Holland Hoole
Hermas... The Greek original disappeared, and it was long known only in a Latin version. But a few years ago a Greek version of the greater part of Hernias was discovered by Simonides in Mount Athos. This is now called the Codex Lipsiensis.1 The character of the discoverer caused it at first to be regarded with suspicion, and it was asserted by Tischendorf that it was in reality not the Greek original, but a translation from the Latin version into Greek, executed in the middle ages. The recently discovered Codex Sinaiticus, however, was found to contain a considerable portion of a Greek version of Hernias substantially the same as that of the Codex Lipsiensis; and as the Codex Sinaiticus can hardly be put at a later date than 520 A.D., it can scarcely be doubted that the Greek version which it contains is the original of Hermas, as it cannot be supposed that the Greek version had then disappeared. ....
1 ... Tischendorf has retracted his objections to the Greek text of the Codex Lipsiensis since the discovery of the Codex Sinaiticus; Hilgenfeld and Canon Westcott accept the Greek as genuine. But it is attacked at length by Mr. Donaldson in his History of Christian Literature and Doctrine, vol. i. p. 309.
Pastor, Graece: assita versione Latina recentiore e codice Palatino (1877)
Gebhardt and Harnack
discussion of Donaldson on Hermas, does it touch on the Sinaiticus problem?
Hermae Pastor. Gr., comm. critico et adnotationibus instruxit, Elxai libri fragmenta adiecit A . (1881)
Zeitschrift für wissenschaftliche Theologie
Zu dem griechischen Schlusse des Hermas-Hirten.
https://books.google.com/books?id=ilM4AAAAMAAJ&pg=PA185 p. 185-186
https://books.google.com/books?id=ilM4AAAAMAAJ&pg=PA334 p. 334-342
https://books.google.com/books?id=ilM4AAAAMAAJ&pg=PA497 p. 497-501
A collation of the Athos codex of the Shepherd of Hermas (1888)
Joseph Armitage Robinson (Spyridōn Paulou Lampros)
The first of these theories was challenged at the time, and was finally disposed of by Tischendorf 's own discovery of the Codex Sinaiticus. From this great Bible he published in 1863 a fragment of the Shepherd, which comprised roughly speaking the first quarter of the book, and presented a text in substantial agreement with that of the Athos MS. The second theory met with a more favourable reception. Anger and Dindorf at once admitted that they had been deceived, and that their edition was absolutely worthless. In 1866 Hilgenfeld re-edited the Greek text from the Sinaitic Codex and the Leipsic materials. In his apparatus he distinguishes to some extent between the two apographon, though he relies mainly on the one which Tischendorf had edited. In 1877 appeared the edition of Gebhardt and Harnack, which gives the Palatine Version in full, and provides an apparatus criticus dealing with the Greek texts and the Aethiopic and Old Latin Versions. It is note-worthy that Harnack (note on p. vii of his Prolegomena) absolutely scorns the apographon which Simonides sold to the Leipsic Library, and collates only the other which was subsequently extracted from him by the police.
Hilgenfeld however in his latest edition (1887) has taken a very different course. The occasion of this new edition is the recent publication by Draeseke of what claims to be the missing Greek conclusion of the Shepherd. This document was printed by Simonides in 1859 together with some other miscellaneous tracts : but by that time he had so completely lost his character,that no one would even look at anything he produced. Draeseke has now rediscovered it, and he asserts its genuineness. 1 Hilgenfeld follows him, and accordingly publishes for the first time a complete Greek text. Harnack on the contrary denounces it as an obvious fraud 2.
Hilgenfeld, then, in his new edition states his belief that Simonides really made both his apographa on Mt. Athos, as he said; but that he probably made them from different MSS. ,the readings of which he somewhat capriciously modified partly by collation and partly by conjecture. This agrees substantially with the account of the matter given by Simonides himself, who always spoke with the greatest contempt of the text which he had kept concealed, as being the recent work of one Abraham the Telian, who had depraved it by the introduction of modern Greek forms.
This latest edition of Hilgenfeld's is a very laborious but amost unfortunate piece of work. In the first place, Harnack is undoubtedly right in saying that the supposed Greek ending is nothing but a loose retranslation from the Latin : and, with regard to the origin and the respective merits of the two apographa, the decision of Tischendorf, which Harnack has always accepted, is now completely confirmed ; on the one hand by the evidence presented by Hilgenfeld himself who has collated both the apographa again for his new edition; and on the other hand by the fresh light which has been thrown upon the subject by the discovery of which I must go on to speak.
1 Hermae Pastor. Graece integrum ambitu primum edidit Adolfus Hilgen-feld. Lipsiae, 1887.
2 Ueber eine iu Deutschland bisher unbekaunte Falschung des Simonides,Theol. Literaturzeitung, 1887, no. 7.
The Oxyrhynchus Papyri, Part 3 (1903)
Bernard Pyne Grenfell, Arthur Surridge Hunt
The Oxyrhynchus Papyri: Texts (1166-1223) (1912)
edited by Bernard Pyne Grenfell, Arthur Surridge Hunt
A papyrus codex of the Shepherd of Hermas (Similitudes 2-9) : with a fragment of the Mandates (1934)
Un nuovo frammento greco del Pastore di Erma (2001)
Shepherd of Hermas Notes (2008)
"It would be nice also to have a follow up blogpost from Martin Heide, with a brief account of his research on the textual transmission of Hermas."
Early Christian Manuscripts: Examples of Applied Method and Approach (2010)
The Egyptian Hermas: The Shepherd in Egypt before Constatnine
THE SHEPHERD IN EGYPT BEFORE CONSTANTINE
Malcolm Choat and Rachel Yuen-Collingridge
p. 192-211 - partial on google
p. 194 - list of papyri
p. 205-211 Appendix: Catalogue of Hermas Papyri from before the time of Constantine
“Assessing the Stability of the Transmitted Texts of the New Testament and the Shepherd of Hermas
"“Labilität und Festigkeit des überlieferten Textes des Neuen Testaments und des Pastor Hermae, demonstriert an wichtigen Textzeugen” “Sacra Scripta” 1/2009
Konrad Martin Heide
"The Shepherd of Hermas in Latin. Critical Edition of the Oldest Translation Vulgata" (TU 173), (2014)
Christian Tornau - Paolo Cecconi (Eds.)