1 The reverse motif is suitable because Strabo, Geography, 16.2.10, reports the presence of the military headquarters, the elephants and the royal stud at Apameia:

In the district of Apameia is a city well fortified in almost every part. For it consists of a well-fortified hill, situated in a hollow plain, and almost surrounded by the Orontes, which, passing by a large lake in the neighbourhood, flows through wide-spread marshes and meadows of vast extent, affording pasture for cattle and horses. The city is thus securely situated, and received the name Cherrhonesus (or the peninsula) from the nature of its position. It is well supplied from a very large fertile tract of country, through which the Orontes flows with numerous windings. Seleucus Nicator (Seleukos I), and succeeding kings, kept there five hundred elephants, and the greater part of their army.

It was formerly called Pella by the first Macedonians, because most of the soldiers of the Macedonian army had settled there; for Pella, the native place of Philip (Philip II of Makedon) and Alexander (Alexander the Great), was held to be the metropolis of the Macedonians. Here also the soldiers were mustered, and the breed of horses kept up. There were in the royal stud more than thirty thousand brood mares and three hundred stallions. Here were employed colt-breakers, instructors in the method of fighting in heavy armour, and all who were paid to teach the arts of war.

2 The Seleukid Era is based on a lunar calendar, beginning with the autumn of 312 BC. It means that if x is a Seleukid year (and x<312) then the corresponding BC time interval is from 313–x to 312–x.

The beginning of the Seleukid Era was set as follows: In 311 BC, shortly after capturing Babylon, Seleukos I Nikator began the enumeration of his satrapal years there. However, after his decisive victory over Antigonos Monophthalmos in 307/6 BC, he backdated his “fictitious” first regnal year to coincide with Nisanu 1, 311 BC (New Year’s Day in the Babylonian calendar). This marked the antedated epoch of the Seleukid calendar according to the Babylonian reckoning. Later in 305/4 BC, when Seleukos I took the diadem and assumed the royal title “King”, he retained the numbering of his regnal years in Babylon but employed the Makedonian calendar and thus pushed his accession year back to Dios, 312 BC (Dios was the first month of the Makedonian calendar; it corresponds to October-November). This became the antedated epoch of the Seleukid era on the Macedonian calendar. (Assar, Recent Studies in Parthian History, Part I, p. 6)

The Seleukid Era was used at least until the first century AD in some Eastern countries.

3 The term Pompeian era is used for the civic era specific for Antioch and its territory which was adopted after Syria became a Roman province in 64 BC. The first year of this era was backdated to 66/5 BC. Thus, if x is a Pompeian year then the corresponding BC time interval is from 67–x to 66–x. See Butcher, CRS, pp. 302 and 312.