Mithradates I and the Evolution of the Parthian Silver Drachm

Historical Context

The reign of Mithradates I represents a decisive watershed in ancient Near Eastern history, transforming the Arsacid state from an embattled regional power situated in Parthia and Hyrcania into an expansive empire straddling the Iranian plateau and the Mesopotamian basin. Modern historians and numismatists debate the precise calendar limits of his rule, contrasting the traditional timeline of circa 171 to 138 BC against a revised cuneiform-backed framework of circa 165/164 to 132 BC.

During this pivotal tenure, Arsacid military forces pushed westward into territories previously governed by the disintegrating Seleucid Empire. Around 148 or 147 BC, Mithradates annexed Media along with its strategic regional capital, Ecbatana. By the summer of 141 BC, Parthian troops entered lower Mesopotamia, taking the great administrative hubs of Seleucia on the Tigris and Babylon. When the Seleucid sovereign Demetrius II Nicator mounted an ambitious counter-offensive in 138 BC to restore western authority, Mithradates decisively defeated and captured him.

This rapid expansion brought prosperous Hellenistic poleis, historic Babylonian commercial centers, and diverse Iranian satrapies directly under Arsacid jurisdiction. The imperial administration adapted its monetary program to accommodate these cosmopolitan populations. Retaining the reduced Attic drachm standard ensured seamless integration with existing commercial networks across western Asia, while the coin dies registered a dramatic ideological pivot, shifting from insular steppe traditions to an imperial Hellenistic visual language designed to address both Iranian and Greek subjects.

Obverse Iconographic Composition

Across the known silver drachm series of Mithradates I, the obverse presents a royal portrait that underwent substantial iconographic evolution through three distinct artistic and political phases.

Early Steppe Phase

In the earliest series, categorized as Sellwood Type 9, the sovereign is depicted facing left. The portrait is beardless and youthful, clad in the nomadic soft felt cap known as the bashlyk or kyrbasia. This headgear features characteristic cheek flaps tied beneath the chin or swept back, accompanied by an extended neck-guard, bound together around the brow by a Hellenistic royal diadem. The king wears a spiral torque around his neck and draped royal garments over the shoulders, with the composition enclosed within a circular pelleted border.

Transition Phase

Represented primarily by Sellwood Type 10, the intermediate phase retains the monarch facing left wearing the diademed bashlyk. However, the profile undergoes a notable physical modification: the portrait displays a short, trimmed Iranian beard. Secondary adornments include an ear ornament, a neck torque, and draped mantle folds, framed inside a dotted circular border.

Mature Hellenistic Imperial Phase

With the consolidation of imperial territory in Media and Mesopotamia, the royal portraiture abandoned the bashlyk in favor of royal Hellenistic conventions, classified under Sellwood Types 11 and 12:

• Left-Facing Diademed Bust (Sellwood Type 11): The king appears bare-headed, wearing only the royal diadem tied with flowing ribbons at the back of the head. His hair is dressed in stylized, voluminous wavy curls typical of Hellenistic royal portraits, while his facial features display a prominent, neatly trimmed pointed Iranian beard. He wears a torque around the neck and an embroidered chlamys, with the entire bust framed by a Hellenistic bead-and-reel (astragalos) border.
• Right-Facing Diademed Bust (Sellwood Type 12): This parallel mature series turns the diademed, bearded bust to the right. On specific die varieties, such as Sellwood Type 12.3, a vertical composite bow is engraved in the field directly behind the royal neck, uniting Greek diademed majesty with Iranian martial symbolism. The border on this series generally consists of conventional pellets or a linear circle.

Obverse Epigraphy and Inscriptions

The obverse dies across all standard silver drachm issues of Mithradates I are entirely anepigraphic. No royal names, territorial designations, patronymics, titles, or calendar dates appear on the obverse flan.

This complete absence of obverse lettering conforms to the overarching early Arsacid numismatic tradition, in which the obverse was reserved exclusively for the royal image and framing borders. All administrative, dynastic, and titular epigraphy was relegated systematically to the reverse field.

Reverse Iconographic Composition

The reverse field of the silver drachm predominantly features the central dynastic badge of the Arsacid dynasty, supplemented by a rare civic-inspired Hellenistic type struck at Seleucia on the Tigris.

The Standard Dynastic Archer Type

On standard issues spanning Sellwood Types 9 through 12, the reverse composition depicts an archer seated facing right:

• Figure and Dress: The archer is attired in traditional nomad equestrian garments, including close-fitting trousers, a long-sleeved tunic, and a soft bashlyk covering the head and neck.
• Seat: He sits upon an omphalos, the conical sacred stone of Apollo borrowed directly from the reverse iconography of earlier Seleucid royal silver. Within Arsacid visual propaganda, the omphalos was reinterpreted as a seat of dynastic primacy.
• Action and Attributes: The figure holds an extended double-curved composite bow outward with his right hand, resting the lower tip or his left hand toward his knee.
• Iconographic Identity: Classical and modern numismatic scholarship identifies this recurring figure not as the reigning king, but as Arsaces I, the venerated founder of the dynasty. He appears as an idealized heroic progenitor whose presence legitimizes the authority of each subsequent successor.

The Enthroned Zeus Type

Following the capture of Seleucia on the Tigris, an exceptional silver drachm series was minted (Sellwood Type 13.6 and dated variety 13.8) that temporarily abandoned the dynastic archer in favor of Hellenistic civic iconography:

• Central Figure: Zeus seated left upon a backless throne.
• Attributes: Zeus holds an eagle or Nike on his extended right hand and rests his left hand upon a vertical scepter.
• Administrative Elements: The exergue beneath the throne incorporates control monograms or explicit dates recorded according to the Seleucid Era.

Reverse Epigraphy and Inscriptions

All reverse legends across the silver drachms of Mithradates I are composed in the Greek alphabet and written in Koine Greek, employing the genitive case of authority. The epigraphic formula underwent a structural expansion directly correlating with the monarch's territorial acquisitions.

Two-Line Series Legend (Sellwood Type 9)

Drachms representing the early bashlyk series bear a concise two-line vertical formula flanking the central seated archer:

• Script: Epigraphic Koine Greek.
• Language: Ancient Greek.
• Original Lettering: ΒΑΣΙΛΕΩΣ ΑΡΣΑΚΟΥ (occasionally arranged as ΑΡΣΑΚΟΥ ΒΑΣΙΛΕΩΣ).
• Transliteration: Basileōs Arsakou.
• English Translation: "[Coin] of King Arsaces".
• Arrangement: ΒΑΣΙΛΕΩΣ is engraved vertically downwards in the right field; ΑΡΣΑΚΟΥ is engraved vertically downwards in the left field behind the archer.

Three-Line Imperial Series Legend (Sellwood Types 10, 11, 12, and 13)

Beginning with the bearded bashlyk series and continuing through the bare-headed diademed issues and the Seleucia Zeus issues, the legend expands to three lines to incorporate the prestigious title "Great":

• Script: Epigraphic Koine Greek.
• Language: Ancient Greek.
• Original Lettering: ΒΑΣΙΛΕΩΣ ΜΕΓΑΛΟΥ ΑΡΣΑΚΟΥ.
• Transliteration: Basileōs Megalou Arsakou.
• English Translation: "[Coin] of the Great King Arsaces".
• Arrangement: ΒΑΣΙΛΕΩΣ stands vertically on the right reading downward, ΜΕΓΑΛΟΥ is positioned horizontally across the top above the figure, and ΑΡΣΑΚΟΥ runs vertically on the left reading downward behind the figure.

Typology and Documented Variants

The silver drachm coinage of Mithradates I is classified using the typological framework established by David Sellwood, supplemented by references in the Shore and Sunrise collections. The physical parameters of the series adhere to the reduced Attic standard, with drachm weights typically ranging between 3.50 g and 4.30 g, diameters between 18 mm and 21 mm, and a predominant die orientation of 12 o'clock.

Note on attribution limitations: The assignments in this table reflect published classification systems and institutional holdings. Specific sub-varieties, mint assignments, and strike dates cannot be assigned to unseen specimens without direct laboratory examination of die markers, weight, flan thickness, and metallurgic composition.

Scholarly Debates and Attribution Limitations

The numismatic corpus of Mithradates I is surrounded by significant scholarly discourse concerning chronology, royal attribution, administrative geography, and dynastic numbering.

Chronological Frameworks and Cuneiform Evidence

David Sellwood proposed a regnal range of circa 171 to 138 BC, relying heavily on a dated tetradrachm from Seleucia struck in Seleucid Year 174 (139/138 BC). However, more recent research by Gholamreza F. Assar and Edward Dąbrowa reevaluates this chronology using Babylonian Astronomical Diaries and ostraca from Old Nisa. These cuneiform texts demonstrate that Mithradates entered Seleucia in 141 BC and that his administrative authority was recognized in Mesopotamian legal documents as late as 132 BC, supporting a revised regnal span of circa 165/164 to 132 BC.

Reattribution of Early Bashlyk Types

Sellwood attributed all silver issues bearing the title ΒΑΣΙΛΕΩΣ (Type 9) and ΒΑΣΙΛΕΩΣ ΜΕΓΑΛΟΥ (Type 10) to Mithradates I, premised on the assumption that predecessors Phriapatios (c. 185–170 BC) and Phraates I (c. 170–165 BC) did not mint silver coins. Contemporary scholars, including Assar, Nikolaus Overtoom, and Marek Jan Olbrycht, have challenged this view. Stylistic, hoard, and metrological analyses suggest that Type 9 and perhaps the earliest iterations of Type 10 were issued by Phriapatios or Phraates I. Consequently, many modern catalogers classify Sellwood Type 9 under the broader heading of "Phriapatios to Mithradates I."

Arsacid Regnal Names and Numbering Divergences

Because Parthian coins consistently employ the dynastic throne name Arsaces rather than personal names, reconstructing the regnal sequence depends entirely on reconciling numismatic typologies with fragmentary classical and oriental literary sources. This produces numbering discrepancies across catalogues. For example, the king reigning circa AD 10 to 38 is designated Artabanus II in Sellwood's system, but Artabanus III by scholars following the historical narratives of Trogus and Justin. Similarly, research by Fabrizio Sinisi in the Sylloge Nummorum Parthicorum demonstrates that the prince Pacorus, son of Orodes II who died in 38 BC, never issued coins as Great King, requiring the ruler traditionally known as Pacorus II (c. AD 78–120) to be renumbered as Pakoros I.

Mint Marks versus Magistrate Monograms

Sellwood's assignment of specific early Arsacid mint locations, including Hekatompylos, Nisa, Syrinx, and Rhagae, relied substantially on isolated Greek letters and monogram forms appearing on the reverse dies. Modern researchers emphasize that these markings often designate workshop officinae, control magistrates, or moneyers rather than geographic city initials. As a result, geographic mint attributions for early Parthian drachms remain hypothetical working models rather than definitive certainties.

References

1. British Museum Collection Online: Specimen Record OR.8346. Specimen record for AR drachm of Mithradates I, Sellwood Type 9.1
2. British Museum Collection Online: Specimen Record OR.8350. Specimen record for AE octachalkon/bronze issue from Ecbatana
3. Parthia.com: Mithradates I (c. 171 - 138 B.C.) Directory. Types 7 through 13 coin catalogue and specimen database
4. Parthia.com: Sellwood Types and Subtypes Index. Typological concordance and diagnostic subtype listings
5. Numista Online Catalogue: Drachm - Mithridates I / Phraates I (Sellwood 9). Catalogue entry N# 93213, two-line legend reverse
6. Numista Online Catalogue: Drachm - Mithridates I (Seleucia, Sellwood 13.6). Catalogue entry N# 375181, enthroned Zeus reverse
7. A Revised Parthian Chronology of the Period 165-91 B.C. (Assar, Gholamreza F., Electrum 11). Electrum 11 (2006), pp. 87-158
8. Les aspects politiques et militaires de la conquête parthe de la Mésopotamie (Dąbrowa, Edward, Electrum 10). Electrum 10 (2005), pp. 73-88
9. Early Arsakid Parthia (ca. 250-165 B.C.): At the Crossroads of Iranian, Hellenistic, and Central Asian History (Olbrycht, Marek Jan). Brill (2021), Chapter 8: The Early Arsakid Coinage and Concept of Royal Power
10. Sylloge Nummorum Parthicorum, Volume 2: Mithradates II (Curtis, Vesta Sarkhosh, et al.). Austrian Academy of Sciences Press (2020), Introduction and mint methodology
11. Sylloge Nummorum Parthicorum, Volume 7: Vologases I - Pacorus II (Sinisi, Fabrizio). Austrian Academy of Sciences Press (2012), Foreword and ruler numbering revisions
12. Encyclopaedia Iranica Online: Arsacid Coinage (Alram, Michael). Encyclopaedia Iranica article on dynastic coin types
13. Encyclopaedia Iranica Online: Phriapatius (Overtoom, Nikolaus). Encyclopaedia Iranica entry regarding regnal succession and coinage attribution
14. Classical Numismatic Group Feature Auction 132 Archives. CNG Auction 132 (March 2026), Lots 554-556
15. Classical Numismatic Group Electronic Auction 133 Archives. CNG Auction 133 (September 2026), Lots 5673-5675
16. An Introduction to the Coinage of Parthia, 2nd ed. (Sellwood, David). Spink & Son (1980), physical monograph cited as further reading
17. Parthian Coins & History: Ten Dragons Against Rome (Shore, Fred B.). CNG (1993), physical monograph cited as further reading
18. Numismatic Art of Persia: The Sunrise Collection, Part I (Nelson, Bradley R., ed.). CNG (2011), physical collection catalogue cited as further reading