Looks like a Faustina lifetime denarius, maybe Ceres on the reverse? I'm uncertain of its authenticity. If real, it's probably isn't worth very much unless this is some type of special denarius. Someone who knows what they're talking about will be along to help you.
That is not a lifetime issue. It says, "DIVA," which means she had been deified after her death. Faustina Senior was the wife of Antoninus Pius. This is a denarius, RIC 361, BMCRE 417, RSC 101a, RCV 4583. The reverse depicts Ceres standing, raising right hand and holding long torch in left. While I don't have this exact coin, I do have a similar one, also depicting Ceres:
As to rarity, it's common, low-grade, on a ragged flan, and unappealing. Value is perhaps $20, but if you asked me if I'd buy it for $20, seeing as how I don't have it in my collection, I'd pass.
Roman Collector makes a good point here. If you were looking for this coin and had to pay what someone who had it was asking, the price might be $20 but if you owned it and wanted to sell it, you would have trouble finding someone to pay $10 unless they were new and believed anything that old has to be worth more than that. Most people who for some reason want this type will prefer a nicer one and not one that RC correctly describes as "common, low-grade, on a ragged flan, and unappealing." I paid $45 for mine a few years ago but would not go that high today. When I bought it, I was impressed by the fact I did not have the type. Now I am more realistic and realize you don't need them all so we might as well hold out for a prettier specimen or a more interesting type.
You know that those who have the passion for ancients hold a value to these coins as relics of history, beautiful and amazing even actually in any condition. Although this view is just one side of the "coin" so to speak. There is the analytical standard that is used as a measure as well which is also critically important overall. Not everyone gets the passion. I say we must connect to the Muse of Cleo/history and one or two of her holy sisters to really get the gist that these are a part of the scroll of our human history.
Thanks guys. It came into a buddies shop in a bulk deal and he wasn't exactly sure what it was like most non-ancient dudes. You really have to have at least a basic command of Roman history to collect these things.