The coin in our picture is quite amazing. You rarely see them this nice. The strike detail, centering, and surfaces are basically perfect. The tone is called 'cabinet tone' and results from careful storage of this precious piece for years and years. This coin sold for 12000 euros (about $13000 US dollars) during a 2012 auction by respected auction house Art Coins Roma of Rome, Munich, and London. CoinQuest thanks Art Coins Roma for use of their coin photo. It is a beauty.
More 'normal' coins are worth much less than the Roma piece, although this is still a rare coin and brings excellent value when in decent condition. Very approximately:
worn: $300 US dollars approximate catalog value
average circulated: $4000
well preserved: $8000
Of course all coins of this calibre stand on their own merits, not on catalog values. To give a better idea of value of these coins, consider the four images to the right, marked (A), (B), (C), and (D).
The (A) image is a close-up of the Art Coins Roma coin ($13000). You can see the excellent detail, pleasing surfaces, and wonderful eye appeal.
The (B) coin is more like the 'normal' ones you see. It comes from Numismatica ARS Classica and sold for about $2000 during a 2014 auction. The surfaces are dark and the strike is somewhat incomplete, missing part of the Q. Nasidius inscription.
A fragment of a genuine coin appears in image (C). The damage caused tremendous lowering of value to about $50. Even so, Heritage auctioned this piece to a lucky collector during 2014.
Coin (D) is a fake from ForgeryNetwork, worth zero. The pattern is not correct and the coin is cast, not struck.
Note to requester Dan: From your description, your coin is very suspect. You say there is a hole, but genuine coins are unholed. The 'layered' aspect you mention sounds bad, and the coin is a little heavy at 4.45 grams. Normal silver denarius weigh a gram or so less than that.