I’m re-publishing this analysis, first published in 2017, as quickly as I can for the benefit of another scholar who has no particular interest in Voynich studies. Thereafter, I’ll return to the history and course of Voynich studies since 1912.
The author’s rights are asserted.
If the Dioscuri at the head of the image on f.5v* were the seamens’ saviours, the seamens’ bane was a creature represented by a second device, set at the base.
Linnaeus called it “calamitas navium” and the Greeks, teredon. It is also called the ‘termite-worm’ and that is exactly how the device is formed in folio 5v: half as blind ant and half worm, gripping the wood with a white ‘collar’ which in this image signifies at once a removal of a ‘wood”s outer skin (the constant sense of a comparable motif in the botanical images) but also, in this case, the creature’s white, ‘lips’ of shell. With them it gripped and ate through a ship’s hull and any other immersed timber.
The second image (above) shows a large type of teredo known as teredo navalis, but there there were other types of teredo and those infested the Mediterranean in ancient times, just as they do today.
The creature turns brown only after exposure to the air; alive, it is soft and grey-ish. In effect the picture on folio 5v ‘kills it’ and I daresay the Dioscuri were often urged to do the same; the teredon’s boring can render a ship’s hull below the waterline as porous as sponge, and infested ships might founder with all hands, unexpectedly, in the finest weather. 
There is evidence of measures being taken to minimise damage from the shipworm, by Egyptian and Phoenician ships, from as early as the second millennium BC.
The drawing’s allusion to the shipworm is another useful indication of the first maker’s environment and cast of mind. For the ordinary landsman, the mariner’s greatest peril was imagined monstrous – – a great whale, fearful dragon, snarling long-toothed Leviathan or a sea-serpent so huge it could overtake a ship and pick off the crew from the open deck.
Mariners might believe in fabulae, too, but they knew that aside from storm and tempest, or being becalmed, the greatest danger posed a ship and a danger over which they had little control was that little ‘termite-worm’ teredon, gnawing at the wood below and which which despite its small size had an ability to ‘devour’ all at once – ship, men and cargo altogether.
It is evident, then, that the person who first formed the image on folio 5v*, and the persons for whom he made it, had an intimate knowledge of the sea – in the way a practical mariner might, or a ship-owner or some member of a maritime community.
Remedy against that ‘ant-worm’ was limited. A protective cover for the keel or coating the keel with tar, pitch or bitumen were all that could be done.
For seamen of the Mediterranean, sources of tar, pitch and bitumen were not many. One that is often mentioned was near Mosul – a point whose importance will become clearer when we move into the period from the thirteenth-mid fourteenth centuries, at which time, in my opinion, a majority of the matter now in Beinecke MS 408 first entered Latin horizons. Mosul was also to have become, by then, an important centre for the manufacture of astronomical instruments.
During the 2ndC BC, however, Mosul was Nineveh and now a city in the Hellenistic Seleucid kingdom (or -empire), and that dynasty, from the first, had the Dioscuri as its patrons.
One cannot imagine any Mediterranean people, after the 3rdC AD, let alone someone living in fourteenth- or even fifteenth-century Europe, invoking the Dioscuri as protectors of the ship. They would cry for aid to Christ, or to Mary as Stella Maris, or to St.Elmo, or even St.Paul or some other among the saints associated with the seaman.
At the very latest, therefore, first enunciation of the drawing on folio 5v* could be no later than the 3rdC AD, and among other factors are technical considerations which oblige me to give a date of first enunciation for this image around the 2ndC BC. 
Nonetheless, from the last decades of the fourth century BC, the Dioscuri had been patrons of Seleucid lands and thus of the routes linking Asia Minor to India, and sea-routes which were in turn linked to them.
Below, the Seleucid lands (mustard-coloured) in the time of Antiochus I. It is easy to find maps of this sort, but not all are so accurate.
Above its northern limit, on the eastern shore of the Black Sea, stood the town said to have been founded by the Dioscuri and named, unsurprisingly, Dioskurias. It stood on an ancient road whose northern terminus was Tanais, and which passed southwards towards the Persian gulf. I’m grateful to be able to share with readers an archaeologist’s sketch of that ancient road. Beyond Ecbatana another road continued to the Persian gulf where – certainly to as late as the 10thC AD – traders and travellers took ship to travel the maritime ‘spice’ routes. The town’s name was Teredon.
Did the first enunciator intend a parallel, geographic, allusion to be embedded in his paired ‘upper’ and ‘lower’ devices in addition to alluding to the ship and the plant-group we’re yet to dicuss?
I can’t say. There’s not enough in the image visible to me that would allow me to form an opinion on the point. It’s entirely possible, and fits the historical context, but there’s not enough in the image legible to me to permit me a firm opinion, either way. What I can say is that correlation between astronomical and geographical loci is the essence of navigation by the stars across the wastes of sand and sea, and this science is certainly one of the oldest of human sciences, having an attested history among some peoples of 60,000 years. So it’s possible.
What makes it not unlikely in connection with matter in Beinecke MS 408 is that such correlation is indicated in other sections, and principally what I’ll call, altogether, the ‘ladies’ sections.
Since I’ve indicated again quite recently that in my opinion transmission for some, at least, of what is in Beinecke MS 408 first entered the Latins’ horizons around the mid-fourteenth century and did so so due to combined Jewish and Italian interaction, this seems a useful place to see how that interaction worked then in sites of ancient Greek foundation.
By the middle of the sixth century BC, before the birth of Alexander, several Greek colonies lay around the northern and eastern shores of the Black Sea, Dioskurias of course being among them.
By the thirteenth and fourteenth centuries AD, what had been ancient Trapezos was now called Trebizond/Trabzon and had shifted seamlessly from being a polytheist Hellenistic to a monotheist Byzantine Christian community and was now in effect the ‘other’ Byzantine capital. The ancient settlement of Theodosia had been transformed by being assigned to the Genoese as their chief trade-centre, connecting with the overland silk and ‘spice’ routes. The Genoese called it Caffa, and among their other sites of occupation and trade was the old Dioskurias, now known as Sebastopol. There they had a factory, and would have a great warehouse in Trebizond.
Contrary to the campaign of slanders, rumour and ‘pack-attacks’ directed against the Jews of western Europe at this time, the situation in places where Genoa governed, and especially Caffa, was very different. For convenience, here’s a concise description from an online encyclopaedia. I’ll turn in a later post to the mariner-trader-bowmen of medieval Genoa, and to Mosul.
The old synagogue of Feodosiya, thought to be the most ancient in Russia, had an inscription which testified to its construction in 909. Under the rule of the Republic of Genoa from 1266, Feodosiya became the center of the Genoese colonies on the Black Sea. In order to attract merchants from all nations there, freedom of religion was granted for all Christian sects, Muslims, and Jews. The traveler Schiltberg, who visited Feodosiya at the beginning of the 15th century, relates of the existence of two [such] communities in the town – a Rabbanite and a Karaite one. The Jews engaged in commerce and maintained relations with the Near East and Poland. The constitution of the town, proclaimed in Genoa in 1449, called on the consul and city elders to protect the Jews as all members of other religions, “from any robbery, from scheming against their property when one of them died intestate, and from other molestations of the bishop.”
The situation of the Jews remained unchanged when the government of the town was transferred to the Bank of San Giorgio, a powerful financial company that administered the eastern colonies of Genoa (1453–75).‘Feodosiya’ encyclopaedia.com.
That Rabbanites and Karaites should live adjacent to one another but separated by a wall was evidently a very old custom. Benjamin of Tudela describes the same arrangement observed in Pera before Constantinople gave authority over that enclave to the Genoese and indeed when all the allusions in the Voynich map were worked through (a process which took the present analyst more than three years) my conclusion was that the map’s so-called ‘castle’ with its land rising close to either side represents Constantinople and/or Pera as they appeared if one approached the sea-gates, and shortly after the Genoese additions to the Galata watchtower, completed in 1349.
A couple of decades earlier, Pietro Vesconte, a Genoese cartographer, had begun producing maps in the new style of the cartes marine gridded by the ‘rose’; the Majorcan school of Jewish cartographers were to produce, by 1375 a magnificent worldmap in similar style with associated tables, including a perpetual calendar. By 1399, Datini’s agent could commission on behalf of a client four world-maps – he appointed as chief cartographer a Majorcan Jew converso, and as his assistant painter, a Christian of Genoa,
Across the last stage of the overland ‘silk and spice’ roads, into Trebizond, new astronomical matter came from Persia, including an updating of Ptolemy’s Tables of astronomical co-ordinates. They came thanks to Gregory (or ‘George’) Chioniades, and would be brought, eventually, to the mainstream Latins of Europe in the adjusted form given those tables by George Chrysococces in about 1347 – but such material came by an independent route to the Jews of the south-western Mediterranean, as we know from the study made of one manuscript (Sassoon MS 823 . now UPenn LJS 057). It contains an illustrated star-table for the latitude of Perpignan and the year 1391.
By that time astrology was a matter of keen interest in both the Latin and the Byzantine sphere, and it is another pointer to where and for whom the image on folio 5v* was made that it refers to stars, but not to astrology.
The stars in Gemini referenced by the upper mnemonic device in f.5v* are principal stars of navigation; are markers of time and of direction, and in this drawing the Dioscuri are not present as mere tokens but because for the first enunciator and his fellows, the Dioscuri were the iconic ‘saviours’ and protectors of the ship.
Indeed, inherited and reflexive assumptions in Voynich studies notwithstanding, nothing in Beinecke MS 408 expresses or accords with the forms employed in medieval or in classical Roman or medieval Islamic astrology.
The manuscript does not even present a ‘zodiac’ but a series of emblems used to fill the centres of the month-diagrams as note of which constellation rises highest in that month. Not all twelve constellations of the tropical zodiac are included, and some of those that are, are doubled – a first hint, perhaps, of a calendar with customary intercalations. I say ‘perhaps’ for there are other possibilities.
After attempting for some years to be heard in explaining the simple fact that the Voynich month-folios do not present us with a zodiac, I finally turned last year to two persons whose area is not iconographic analysis but, specifically, the history of comparative astrologies.
Each said again, independent of each other and of me, that the month-diagrams are NOT horoscopic charts or anything of that kind – not from the Latin, Byzantine or Islamic astrology. The information was not exactly met with appropriate thanks by the wider ‘Voynich community’ though it’s obviously an important point for our efforts to rightly understand the manuscript and to discard theoretical narratives whose ‘givens’ are increasingly incompatible with modern scholarship.
Past patterns of behaviour by some tenacious theory-holders lead me to think that when the fact is eventually permitted to be mentioned in Voynich arenas, some few – very few – theorists will credit the source while others will attempt to convey an impression that the insight is not new; is their own; or will credit it to some crony.
“Why such shenanigans?” the objective reader may ask. The core problem, as far as I can understand it at all, appears to be that, just as scholarship gave way, years ago, to ‘theory wars’ as primary force, so presently that is giving way in favour of very strange ‘personality war’ where attempting to debate issues of fact and evidence are being re-defined as ‘personality’ conflicts and a person with a question as someone with a ‘personality problem’ and anyone presenting a theorist with a too-difficult intellectual problem is re-defined as having a ‘mental problem’.
It’s an early phase of this new sort of ‘triumph struggle’ in Voynich studies and in terms of sociology not uninteresting. Unproductive for manuscript studies of course, but the ‘personality’ focused seem to have neither time or energy to waste on the slog of research.
And to take a longer view – knowing as we now do that a closely similar phenomenon can corrupt even the political process of a country as great as America, then perhaps what we’re seeing in Voynich studies is just another example of the temper of our times.
Let’s hope not.
And so again to our illustration….
The first enunciator has combined effortlessly information relative to botanical, astronomical and cultural matters and there is nothing to suggest any interest in astrological practices, or any knowledge of Christianity and its saints.
Though knowledge of the Dioscuri and of the two asterisms in Gemini are expressed in the drawing, it precedes the period when monotheism came to be the only acceptable form of religion in lands of the southern and eastern Mediterranean.
Allusion to those stars in the upper mnemonic device in folio 5v* is made in a way easy, oblique and yet precise. Nothing here smacks of the magical or mystical.
This is all the more interesting since we are told that when the Seleucid capital was moved to the newly-built Antioch, Seleucus I Nicator, who had been a general in Alexanders army, brought many Babylonians to live there. Commenting on this Cumont made the usual error of his own time in imagining any mention of stars and constellations must signal ‘astrology’ but there’s no doubt that the Seleucids became aware of Babylonian practice.
About the Arabs’ lunar mansion system great deal of solid scholarly research has been done, including research into its pre-Islamic version. It is understood that an ancient Yemeni agricultural calendar (studied by Serjeant) was pre-Islamic in origin, but more relevant for our present subject is that the series also served as the horizontal axis for a mariners’ navigational grid and was still being employed in that way among some Arab master-navigators as late as the fifteenth century.
There is no evidence that the Romans knew the lunar mansions’ stars in that way but we have indications of some such system being known to the Phoenician and/or Cretan mariners prior to the Romans’ advent and the Phoenician genocide. I’ll not dilate on that point.
To most Latins of Europe the manzil were unknown; to those who learned of them first through the Picatrix, they were regarded as an occult system. None of this is indicated in the slightest by what we see on folio 5v*
Reading the top mnemonic device on folio 5v* – salient points are that Greek-speakers of the Hellenistic period knew the stars in Gemini and regarded the Twins (Dioscuri) as the mariners’ patrons; associated them with the kingdom which formed a bridge between the Mediterranean, India and the Persian gulf.
Dioskuri[as?] to Teredon.
 There is a giant teredon found near Sumatra; it doesn’t live in wood but in the muddy bottom, though one doubts if foreign seamen would have trusted to that difference, even if they knew it.
For those who enjoy biology, there’s an ongoing scientific study of the teredo and the site has nice photos and diagrams. (here).
 We are now in a rarified area of modern scholarship. Two sources consulted should be mentioned: Alwin G. Steinmayer and Jean M Turfa ‘Effects of shipworm on the performance of ancient Mediterranean warships’, International Journal of Nautical Archaeology Vol. 25, Issue 2 (May 1996) pp.104 – 121; and reply by Cynthia M. Harrison, ‘A note on the care and handling of triremes’, International Journal of Nautical Archaeology, Vol. 32, Issue 1 (August 2003) pp.73-79. Excavation of some pre-Hellenistic Greek shipyards has revealed keen awareness of risk from the Mediterranean species. Our knowledge of woods used in ancient and classical shipbuilding in the Greek world is extremely scarce, and what there is refers to cedar of Lebanon and to what are believed species of oak. But there is so little to go on. [added note 17th Feb. 2022 – One paper on the subject is online as a pdf: Johann Müller, ‘Tree species used in historical shipbuilding and their risk of being attacked by Teredinidae’. For the last-named paper I’ve had no opportunity to ask a specialist’s evaluation and in this highly specialised subject, I can offer none myself.
’technical consideration’ – not least of which is the shifting assignments of star-names in indigenous astronomy as the precession of the equinoxes changed the sky’s appearance – at a rate of about 50.3 arcseconds per year. By the Islamic period the ‘bent or turned around’ description was being applied to stars in the second figure of Gemini, where the maker had still connected that idea with the first. The name anciently given Orion as the ‘great house’ (pharaoh) and its name as Jauza had also become, for the Arabs, descriptions for Gemini – while application to Orion was not wholly forgotten… and so on.
 Karl A. F. Fischer, Paul Kunitzsch and Y. Tzvi Langermann, ‘The Hebrew Astronomical Codex MS. Sassoon 823’, The Jewish Quarterly Review, New Series, Vol. 78, No. 3/4 (Jan. – Apr., 1988), pp.253-292. and subsequent publication.
 According to the Yemeni/Soqotran calendar reported by Serjeant, al Han’ah marks the lunar month beginning on January 4th, save in Hadramawt, where the month begins on January 1st. The Soqotri name, he gives as Ma’ōdīf. al-Dira’ is called in Soqotri Franzak, and begins on 17th. January. Note that the advent of Islam saw the older lunar calendar ‘frozen’ and we may not presume to apply the same dates after c. 8th-10thC AD as were in effect before that time, when irregular intercalations were still regularly used. R.B. Serjeant, ‘A Socotran star calendar’, Irvine et.al. (eds.), A Miscellany of Middle Eastern Articles.. (1988) pp. 94-100. Reproduced as Paper IV in R.B. Serjeant, Farmers and Fishermen in Arabia: studies in customary law and practice edited by G. Rex Smith (Variorum) (p.96)