Bingen, J. "Le trésor de tétradrachmes attiques de style Pi" in MIGRA I (Gent, 1975), pp. 161 - 170.
Bingen, J. "Le trésor monétaire Thorikos 1969" in Thorikos VI. (Brussels, 1973), pp. 7-59.
Flament, C. Le monnayage en argent d'Athènes. De l'époque archaïque à l'époque hellénistique (c. 550-c. 40 av. J.-C.). (Lovain-la-Neuve, 2007).
Head, Barclay. Catalogue of Greek Coins in the British Museum, Attica - Megaris - Aegina. (London, 1888).
Kroll, John H. The Greek Coins. The Athenian Agora, vol. XXVI. (Princeton, 1993).
Kroll, John H. "The Reminting of Athenian Silver Coinage, 353 B.C." in Hesperia Vol. 80 (2011).
Nicolet-Pierre, H and J.H. Kroll. "Athenian Tetradrachm Coinage of the Third Century BC" in AJN 2 (1990). pp. 1-35.
Sverdrup, Harald U. The history and catalogue of the tetradrachms of Athens. (Stockholm, 2010).
Svoronos, J. Les monnaies d'Athenes. (Munich, 1923-26).
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The name Pi-style refers to the floral helmet ornament on the obverses, which on the most advanced and numerous coins in the series resembles the Greek letter pi (P) bisected by a long central tendril. J Bingen published the first stylistic analysis of the Pi-style tetradrachms (Thorikos and Bingen Pi-Style). On the pi-style reverse, the alpha is positioned below the head, its left diagonal wedged in the notch where the head meets the body, thus permitting every pi-style tetradrachm to be distinguished from earlier specimens of the same denomination instantaneously. Pi-style tetradrachms were probably struck from 353 to c. 297 B.C.
J.H. Kroll determined that all Bingen pi-style I - IV and some pi-style V tetradrachms were overstruck on folded and hammered flans and the first pi-style tetradrachms were likely produced in a frantic restriking of demonetized older tetradrachms in 353 B.C. (Kroll Pi-Style).
"Combining evidence from Athenian silver coins, an unpublished Agora inscription, and several accounts concerning historical figures, this article reconstructs the Athenian program of 353 B.C., whereby all of the larger-denomination silver coinage in the city was demonetized and called in for restriking as a means of raising revenue during the fiscal crisis in the aftermath of the Social War. The folded-flan technique and erratic, substandard appearance of the resulting "pi-style" coins, attestations of their hurried production in that year, were retained in all subsequent Athenian silver coinage down into the 3rd century as recognized attributes of good Athenian money." - Abstract for John H. Kroll's "The Reminting of Athenian Silver Coinage, 353 B.C." in Hesperia Vol. 80 (2011).
The last pi-style (pi V) tetradrachms were probably struck in 297. The last Athenian pi-style (pi V) coins were gold staters minted by the Athenian tyrant Lachares in c. 296 - 295. Demetrius Poliorcetes captured Athens in 294 B.C.
Athens' demonetization and restriking program was apparently very successful. Third century hoards found at Athens do not include 5th century tetradrachms and include very few of the pre-demonetization early transitional type.
The chart below, from Kroll's article (Kroll Pi-Style), page 233, shows Bingen's phases of the pi-style helmet ornament.
Differentiating between Bingen's pi-style types can be difficult because they are not very dissimilar and because the ornament is often partially off the flan. There are also examples that are hard to categorize even when the floral ornament is clear. The issue of the different types undoubtedly overlapped to a considerable degree. When new dies with a different floral ornament were introduced, the old dies were still used until worn out or damaged. Most dealer catalog and auction listings do not differentiate between the transitional and the pi-style types and very often date all transitional and pi-style tetradrachms c. 393 - 297 B.C. Differentiating between types Pi III and Pi IV is particularly troublesome. Even Kroll describes them as the "pi III-IV grouping," puts photographs of the two types on the same figure, and does not attempt to identify which of the examples are type III and which are type IV. It is, however, possible to identify the specific pi-style type of some specimens and to date them more precisely, as discussed below. For comparison, an example of an earlier classical (old style tetradrachm), a preceding early transitional tetradrachm type, and a later quadridigité type tetradrachm are also included below.
On the classical old-style tetradrachms, Athena has an archaic almond shaped eye, that appears to unnaturally face the viewer. This is the "all-seeing" eye of the archaic ancient goddess. Athens maintained this archaic style well into the classical period primarily because their coins were so popular that any change seemed unnecessary and perhaps risky. On the classical old-style tetradrachms, the floral helmet ornament is composed of four lines: a long, axial vertical, a curved horizontal that crosses it at the top, and two short lower tendrils that spring diagonally out from the intersection of the vertical and horizontal tendrils.
The early transitional tetradrachms introduced a more natural, eye-in-profile, and more feminine portrait. The early transitional type continued the a relatively naturalistic form of the floral ornament, similar to that on the classical tetradrachms. The lower tendrils of the floral ornament are short arcs, located lower and separated from the upper tendrils, and often detached from the rest of the ornament. The first pi-style types, discussed below, were struck with the same obverse dies used for the transitional tetradrachms. All the various pi-style tetradrachm types can, however, be distinguished from the early transitional tetradrachms by a lower position of the alpha on the reverse, below the head, its left diagonal wedged in the notch where the head meets the body. On the early transitional types, the A on the reverse is higher, as seen on the example above. Other features include a pellet above the earring (sometimes called an "ear button"), and two rows of feathers (pellets) to the right of the owl's beak. Early transitional tetradrachms were struck on cast flans.
References: Kroll Pi-Style p. 241, fig. 4; SNG München 90, 92, 98, 99; SNG Delepierre 1470, 1472, 1473; SGCV I 2537; BMC Attica pl. V, 5; Svoronos Athens pl. 19: 13 - 21, 25 - 26, 32 and pl. 20: 1; Kroll Athenian Agora XXVI pl. 2, 15a, 16n; van Alfen New pl. 8: 21, 24, 26, 29; SNG Cop -
The first pi-style tetradrachms, struck immediately after the demonetization of older Athens tetradrachms, were struck with the same obverse dies used for the early transitional type. The lower tendrils of the floral ornament are short arcs, detached from the rest of the ornament. Other features, which are shared with the early transitional type are a pellet above the earring and another on the owl's forehead, and two rows of feathers (pellets) to the right of the owl's beak. All the pi-style types can, however, be easily differentiated from the early transitional types by the lower placement of the A on the reverse, below the owls head, its left diagonal wedged in the notch where the head meets the body. Pi-style I tetradrachms are all struck on folded flans. After the demonetization, new coins would have been needed immediately. The older de-monetized tetradrachms were folded and hammered to create new flans for restriking. This was, apparently, quicker and cheaper than melting the old coins and casting new flans. The Pi I type was probably only struck until the existing dies wore out, perhaps for only a few weeks or months in 353 B.C.
References: Kroll Pi-Style p. 242, fig. 5; Flament p. 126, 1; SNG München 94; Svoronos Athens pl. 19: 23, 27, 29; pl. 20: 23; Kroll Athenian Agora XXVI pl. 2, 15b, 16a - l; van Alfen New pl. 6: 10; SNG Cop -; SNG Delepierre -
On the Pi II type the floral ornament has not yet evolved into a complete pi shape; it is often closer to a lis. The upper tendrils of the floral ornament are formed by a single continuous curved line intersecting the central tendril (later this will become the upper bar of the pi shape). The lower tendrils are longer than the earlier Pi I type (these will later form the sides of the pi shape). The lower tendrils originate from or near the angles formed by the intersection of the central upper tendrils and the central tendril, the lower tendrils curve and flare outward from the vertical axis for all or nearly all of their length. Pi II has a pellet above the earring on the obverse, and two columns of pellets (feathers) to the right of the owl's beak on the reverse. All Pi II tetradrachms are struck on folded flans and were probably struck shortly after the demonetization of 353 B.C.
References: Kroll Pi-Style p. 243, fig. 6; Flament p. 126, 2; SNG München 91; SNG Delepierre 1469; BMC Attica pl. V, 6; Svoronos Athens pl. 20: 13 - 14; SNG Cop 64; van Alfen New pl. 8: 28; Kroll Athenian Agora XXVI -
The Pi III type introduced the true pi-style floral ornament. The lower tendrils have moved outward from the central tendril, and originate from and perpendicular to the curved horizontal line forming the upper tendrils; they parallel the central tendril for most of their length before flaring outward. The central tendril can be exceptionally long, extending down to Athena's ear. Pi III may or may not have a pellet above the earring on the obverse, and have one or two columns of pellets (feathers) to the right of the owl's beak on the reverse. All are struck on folded flans, often elongated oval shaped flans (nicknamed "logs").
References: Kroll Pi-Style p. 244, fig. 8; Flament p. 126, 3; SNG Cop 63 (round flan) and 64 (elongated flan); SNG München 96; SGCV I 2547 (elongated flan); SNG Delepierre 1474 (elongated), 1479 (round flan); Svoronos Athens pl. 20: 2, 4, 5; van Alfen New pl. 7: 19 - 20; Kroll Athenian Agora XXVI -
Types pi III and pi IV are difficult to distinguish. The only consistent difference is the lower/outside tendrils (sides of the pi) are further outward from the central tendril and from each other. Often, but not always, the lower/outside tendrils are about the same length as the as the perpendicular curved line representing the upper tendrils (top of the pi). The central tendril can be exceptionally long, even longer than pi III, extending down to Athena's ear. All are struck on folded flans.
References: Kroll Pi-Style p. 244, fig. 8; Flament p. 127, 4; SNG Delepierre 1475, 1481; Svoronos Athens pl. 20: 27, 28, 33; Kroll Athenian Agora XXVI -; van Alfen New -; SNG Cop -
A lower/outer tendrils (sides of pi) have about the same length as the curved line representing the upper tendrils (top of the pi). This is often described as a square shape, but it is not necessarily particularly square. The central tendril is shorter, about he same length as the outer tendrils, and reaches no farther than and most often intersects the upper edge of the helmet visor. Pi IV may or may not have a pellet above the earring on the obverse, and have one or two columns of pellets (feathers) to the right of the owl's beak on the reverse. This type has been found in hoards dating to 330s, indicating the type was introduced in the 340s. Some are struck on folded flans, few but some on oblong flans. Most are struck on cast flans. This may indicate that the pi-style evolved to pi V type early, even before the frantic pace of demonetization and restriking ended, or alternately restriking may have continued alongside striking new flans for some time. The examples struck on cast flans are probably struck on new silver obtained through new mining leases at the Laurion mines initiated by the Athenian statesman Eubolos, who was influential from 355 to 342 B.C. Freshly minted examples of Pi V tetradrachms have been found in hoards dated to the early years of the 3rd century B.C.
References: Kroll Pi-Style p. 245, fig. 9; Kroll Athenian Agora XXVI pl. 2, 15c - d; Flament p. 127, 5; SNG München 93; SNG Delepierre 1476 - 1477; BMC Attica pl. V, 4; Svoronos Athens pl. 20: 15, 16, 25; van Alfen New pl. 8: 32; SNG Cop -
Quadridigité style tetradrachms are distinguished by the floral ornament on the helmet, which ends in a shape somewhat resembling four fingers on a hand. The owl never has a pellet between the eyes and the sides of the A are curved and the cross bar does not close the letter. This type was also struck on folded flans. The significant stylistic differences between this quadridigité style and the preceding pi-style indicate the mint was probably closed during domination of Athens by Macedonia, beginning under Demetrius Poliorcetes, from 294 - 286 B.C. The quadridigité style was probably issued from c. 286 when Athens joined the anti-Macedonia coalition in revolt against Antigonus Gonatas and received a gift of silver from Ptolemy of Egypt and allies, until, during the Chremonidean War, Athens was besieged beginning c. 263 and starved into surrender in c. 262 B.C.
References: Flament p. 133; SNG München 145; Svoronos Athens pl. 21: 26; pl. 23: 2-3; Kroll Athenian Agora XXVI pl. 3, 22a - b; SNG Cop -; SNG Delepierre -