There are many eras of ancient cities in the select box of calendars (creation/modification page of coins/banknotes/exonumia).
Perhaps it can be grouped by region (using groups of options, or adding the group name at beginning of each option).
For example, I saw these groups:
- Anatolian cities (or Ancient Greece cities?): https://en.wikipedia.org/wiki/Anatolia
134 Alabanda era (for example, rename to "Anatolian cities - Alabanda era")
135 Alexandria Troas era
136 Anazarbus era
133 Ancient Greece - Aegospotami era
138 Aspendos era
143 Eusebia era (location not sure)
145 Isinda era
146 Laodicea era
147 Magydus era
281 Nicaea - Lysimachus era
149 Oenoanda era
150 Perga era
151 Pergamon era
152 Phaselis era
158 Sillyon era
159 Sinope era
160 Termessos era - Ancient Greece cities: https://en.wikipedia.org/wiki/Ancient_Greece
141 Demetrias era
274 Kition - Pumiathon era
196 Korone era
154 Samos era
161 Thessalonica era
165 Zankle era (located in Sicily?) - Levantine cities: https://en.wikipedia.org/wiki/Levant
137 Ashkelon era
148 Marisa era
347 Sidon - Abdashtart I era
351 Sidon - Abdashtart II era
346 Sidon - Ba'al Sillem II era
350 Sidon - Evagoras II era
348 Sidon - Mazaeus era
349 Sidon - Tennes era
157 Sidon post-Alexander era
156 Sidon pre-Alexander era
352 Tyre - Abdashtart of Tyre era
353 Tyre - Azemilcus era
163 Tyre era - Mesopotamian cities: https://en.wikipedia.org/wiki/Mesopotamia
155 Seleucia era - Roman cities: https://en.wikipedia.org/wiki/Roman_Empire
164 Viminacium era
I am not sure location of
- 144 Gaba era (from Persia (Mesopotamia) or Levante?)
- 162 Tripoli era (from Lebano (Levante) or Greece?)
Also, perhaps these can be grouped into
- Hindu calendars:
62 India - Fasli era
44 India - Kollam era
61 India - Mauludi era
100 India - Tripura era
40 Nepal - Saka era
69 Nepal Sambat
363 Shaka era
14 Vikram Samvat