In Numismatic and some other realms, I've learnt that a coin,for instance, could be worth a hundred or even a thousand coins. Every beginner may need that lesson. Good luck anyway.
I agree with most of what is said above. The coins are common late Roman bronze coins. If you are asking, can you make money buying them at $20. The answer is no. If you are looking to form a small & inexpensive collection of coins that are 1800 years old, a few of these would be a good start. Buy only one per ruler. Pick coins in the best condition for each ruler: details on both the obverse and reverse, letters you can read and coins that look interesting to you (see one that spoke to me below). Before you spend a lot, find a book or web site on Roman Imperial coins. Handbook of Roman Imperial Coins by Van Meter is good and normally inexpensive on line. I bought this one on line for $80 because I wanted the scale on the reverse. I have bought others is similar condition at coin shows for $10 - $20.
It was a difficult decision but I finally decided on the large Maxentius that many of you recommended. Perhaps not the most interesting coin, but it's scratched the ancient itch that I've had since giving my girlfriend a histiaia tetrobol for Christmas. I'm looking forward to researching this coin and learning more about Rome in the process. Thanks for everyone's help!
Exactly! You will discover who the two figures represent and why they have stars above their heads. Your coin is attractive but has one fault that bothers some of us more than others. When you research you will discover what is missing and why some of us care. We could give these answers but you will be better served if we just suggest you look at coins from online resources and ask all the questions you can. When you are stuck on an answer, return here for help. A secret of this list is many more here will want to help people who seem interested in learning to help themselves and, later, help others when the question comes up again. One of mine is a slightly different type. Both are what I consider collectible coins and only a small sample of similar coins from this period in history. Only you can decide if you 'need' both for comparison (and a dozen other types he issued) or only one coin as a representative of Maxentius. Time will tell.