On the meaning of AG in OPUS AG II, it could stand for Aktiengesellschaft, a German word somewhat comparable to our Inc. or Incorporated. I did not see the original medal, but perhaps it was German/Austrian/Swiss?

Regarding obscure translations, there was a series of articles in The Numismatist entitled Coin Mottoes and Their Translations, by Stuart Mosher. It started in April 1948 and ended in September 1948.

It is 35 pages of mostly Latin mottos and their English meanings. From them, many of the abbreviations can be worked out. It was a blessing when I first started collecting older coins, but is poorly known now due to the number of years since it was published. Just copying this data onto a website (with ANA permission) would be beneficial for many collectors, since there are so may translations in that series of articles.

Additional information, if permission can be obtained, from the introductory sections of Sear’s Roman Coins and their Values, and especially Van Meter’s Handbook of Roman Imperial Coins, would provide a great deal of background on Roman Latin mottos and abbreviations.

Combining all three would provide all the information on Latin inscriptions and abbreviations that most people would need for 95% of their coins.