NOW – Dollars in circulation (M1)
THEN – Silver content of a Roman Denarius
Quoted from: https://en.wikipedia.org/wiki/Denarius#Value,_Comparisons_and_silver_content
Silver content plummeted across the lifespan of the denarius. Under the Roman Empire (after Nero) the denarius contained approximately 50 grains, 3.24 grams, or 1⁄10 (0.105ozt) troy ounce. The fineness of the silver content varied with political and economic circumstances. From a purity of greater than 90% silver in the 1st century AD, the denarius fell to under 60% purity by AD 200, and plummeted to 5% purity by AD 300. By the reign of Gallienus, the antoninianus was a copper coin with a thin silver wash.
Remember, after the Roman Empire dissolved it was replaced with tribalism, superstition and the christian cult of fear!