Did Armenians have and use an alphabet before as the common knowledge tells us Mesrop Mashtots “created” an Armenian alphabet? There is evidence that comes to support such an assertion.
One of the Classical accounts about the existence of an Armenian alphabet comes from Philo of Alexandria (20 BCE – 50 CE), who in his writings notes that the work of the renowned Greek philosopher and historian Metrodorus of Scepsis ( ca. 145 BCE – 70 BCE),On Animals, was also translated into Armenian. Metrodorus was a close friend and a court historian of the Armenian Emperor Tigranes the Great. Amongst his great works, Metrodorus also wrote the biography of the King of Kings, Tigranes the Great. Another Third Century Roman History and Church theologian, Hyppolytus of Rome (170-235 CE), in his Chronicle, while writing about the history of the reign of his contemporary, Emperor Alexander Severus (reigned 208-235 CE), mentions that the Armenians are amongst those nations who have their own distinct alphabet.

Philostratus the Athenian, a renowned sophist of Second and Third centuries AD in his The Life of Apollonius of Tyana, wrote:
“And they say that a pard was once caught in Pamphylia which was wearing a chain round its neck, and the chain was of gold, and on it was inscribed in Armenian lettering: ‘The king Arsaces to the Nysian god.’” (Philostratus, The Life of Apollonius of Tyana, Book II, Chapter II, pp. 120-121, tr. by F. C. Conybeare, 1912)
According to the Fifth Century Armenian Historian Movses of Khoren, Bardesanes (154-222 CE) of Edessa, who founded the Gnostic current of the Bardaisanites, went to the Armenian castle of Ani and there read the work of a pre-Christian, Armenian priest by the name of Voghyump, written in the Mithraic (Mehean or Mihrean lit. of Mihr or of Mithra – the Armenian national God of Light, Truth and the Sun) script of the Armenian temples in which, amongst other histories, an episode was noted of the Armenian King Tigranes VII (reigned from 144-161, and again 164-186 CE) erecting a monument on the tomb of his brother, the Mithraic High Priest of the Kingdom of Greater Armenia, Mazhan. Movses of Khoren notes that the renowned scholar Bardesanes, translated this Armenian book into Syriac (Aramaic), and later also into Greek. Another important evidence for the existence of a pre-Mashtotsian alphabet is the fact that the Armenian heathen pantheon included Tir, who was the Patron God of Writing and Science.
A 13th century Armenian historian, Vardan Areveltsi, in his History, notes that during the reign of the Armenian King Leo the Magnificent (reigned 1187-1219), artifacts were found bearing “Armenian inscriptions of the heathen kings of the ancient times…” The evidence that the Armenian scholars of the Middle Ages knew about the existence of a pre-Mashtotsian alphabet can also be found in other medieval works, including the first book composed in Mashtotsian alphabet by the pupil of Mashtots, Koriwn, in the first half of the Fifth Century. Koriwn notes that Mashtots was told of the existence of ancient Armenian letters which he was initially trying to integrate into his own alphabet.
Most of the ancient artifacts have either been lost or destroyed in the ravages of time. We must remember that what we have today and what we know is merely a few percent of the total accumulated cultural heritage of many millennia. Therefore, it is only a matter of time that new evidence, including various artifacts, including possibly ones baring inscriptions made in Pre-Mashtotsian, “mehean” script would perhaps be unearthed, and thus, would further shed light on this important topic and come to complete the written evidence that is currently at our disposal that speaks in favor of the existence of a pre-Mashtotsian Armenian alphabet.
Gevork Nazaryan, Armenologist, Historian (http://www.armenianhighland.com/index_light.html)