VIII. B.C. 27--A.D. 268. _Period of Latest Decline of Art._ The Empire. Augustus--Gallienus. § OF THE METALS OF WHICH COINS ARE COMPOSED. The coins of the ancients were of various metals, of which the following need only be specified. 1. _Gold_, distinguished in numismatic works by the abbreviation [AU] (for aurum). 2. _Electrum_, a compound of gold and silver. EL. 3. _Silver._ AR (argentum). 4. _Billon_ and _Potin_, alloys of silver and bronze. Bil. and Pot. 5. _Bronze._ Copper with a percentage of tin. Æ (æs). § OF THE TERMS USED TO DEFINE THE VARIOUS PARTS OF A COIN. The front or face of a coin is called the _obverse_. Obv. The back is called the _reverse_. Rev. The principal device or object represented on a coin is called the _type_. The area or space between the type and the circumference is called the _field_. The lower portion of the area of a coin beneath the type and separated from the rest of the field by a horizontal line is called the _exergue_. Ex. Small objects represented either in the field or the exergue as adjuncts to the main type are called _symbols_. Portions of a coin which are sunk below the level of the surface are said to be _incuse_. § OF THE TYPES OF GREEK COINS. The types of Greek coins were from the earliest times down to the age of the successors of Alexander almost exclusively religious. The reason for this is not far to seek. In an age of simple faith the head of a god upon the coin was the best of all guarantees for purity of metal and good weight. The gods were, so to speak, invoked by the State to vouch for the good quality of its currency, in the same way as State decrees often began with the formula “_In the name of the gods_.” There is, moreover, some reason to think that the earliest coins were struck within the sacred precincts of the Temple treasuries, as being holy places, secure from plunder and inviolable. In the most ancient period the principal or obverse type is generally some animal or object sacred to or emblematical of that god whose worship was prevalent in the city in which the coin was issued. Subsequently the head of the deity himself was usually placed upon the obverse of the coin, while the reverse side was occupied by the object emblematical of his worship. Frequently, too, the head of one principal deity appears upon the obverse, and, either the entire figure or the emblem of some other, generally local divinity, on the reverse. The chief exceptions to the above rule are the so-called _agonistic types_, or types referring to the games such as the victorious quadriga on the money of various Sicilian cities. These types are commemorative in a general way of victories in the Olympian or other local games, but it is hardly ever possible to refer them to any particular victory.