In ancient times, the Athenian owl coin was perhaps the first standardized currency  to be used over a wide geographical area, and circulated for over 200 years. Today, they are a symbol of the artistic beauty found on many ancient Greek coins. The following is a study of  two owls, the first from the the early period of Greek coinage around 400 BC and the second from around 160BC. Both are silver tetradrachms, a standard unit of currency.

An Early Period Athens Owl

Most Greek coins were hand struck using dies and evidence of this striking is easily seen on this coin's obverse and reverse. The  first image below shows the lower part of the owl's breast, legs, and tail, all of which are outlined with a low rise ridge of metal produced when the coin was struck. The ridges are caused by plastic flow of the metal under extreme pressure.  The red arrows point to areas where  there appear to two parallel ridges, which might indicate that the coin was struck twice. Small edge cracks are also seen near the owls feet.  Weight 17.14g.

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On the obverse, evidence of plastic flow is seen in a halo of fine tendrils that surround the owl's head. The halo is most prominent on the left side where it streatches as far as the fig leaf feature on the far left between the two arrows.

There is also ample evidence that suggests the metal is quite old. The coin is thick and the rim has a rather lumpy metal appearance. Parts of the rim have what looks like a compressed crystalline structure made of many find nodules pressed flat by the striking. The nodules probably formed as the metal cooled and solidified before it was struck. Red arrows point to the nodule areas.

Evidence of metal aging can be seen in the reverse field from a series of deep microscopic fissures. These fissures follow along the lines of possible stress cracks in the metal where corrosive forces can easily attack into the metal. Such corrosion likely occurs over a long period of time. The red arrows run in the direction of the stress crack.

Late period tetradrachms were struck on larger but thinner planchets but retain the superbly high relief features seen on the earlier owls. The facial portraits on some of these coins are so beautiful they almost look like photographic images of real people. The coin's weight is typical at 16.91g.

Micro pitting is seen along probable stress boundaries in the field in a region roughly outlining the face of the portrait. These pits tend to form along lines, which are particularly clear on the left.

One of the most interesting features is perhaps a die crack at about 10 o'clock and two missing dots along the rim. The crack runs in the direction of the red arrows in the image. The surface of the metal below the arrows is slightly raisesd relative to the area above the red arrows, typical of a die crack.