I received it as a Christmas present from my wife in 1996. I knew enough to see it was Constantine the Great, but what could this "PROVIDENTIAE" mean??
I went to my favorite internet search engine at the time, altavista, and searched for the word, providentiae. There was not one single hit! This is probably the most common ancient coin type in existence. There was an obvious lack of information on ancient coins on the web, a vacuum since filled by my own labors and that of many others.
What a different 10 years makes. Now [October, 2007], trying that same search on Google.com, there are nearly 4000 hits... four thousand websites, most of which illustrate, explain, or are trying to sell one of these coins.
So, what does PROVIDENTIAE AVGG mean? There isn't a total concensus, but I believe that the inscription is saying that the gods have led the leaders to provide for the peoples' defense, as embodied by the military fortification pictured.
I find it extremely apropos - uncanny, in fact! - that this coin carries an message of divine guidance. It led me to the largest project of my life, a website called WildWinds.com.
The following pages are an attempt to provide a short guide to explain how to make use of this amazine font of information on ancient coins, both here on WildWinds and elsewhere.