Debasement of the Denarius

Higashiyama

Wikipedia has an excellent overview of the denarius, including a very useful table showing the history of weights and fineness:

https://en.wikipedia.org/wiki/Denarius

However, there is not quite enough detail to allow a collector to ascertain fineness, given a particular denarius example. (for example, it lists fineness as about 83.5 % from 193-235, dropping to 48 % in 241. If I have a particular coin, such as a Gordian III denarius, are you aware of a resource that would allow me to determine fineness?) I guess I could buy a sigma machine -- that might be fun! In any case, in building my Roman Imperial collection, I'm working on coins from the transition to crisis in the early part of third century, and it would be interesting to know the fineness of the silver coins I am acquiring. NGC tells you the mass, but that's only part of the story!

Thanks for any thoughts or directions!

Sapyx

Fineness of Roman coins, even at the height of its strength and stability, was always somewhat variable - the best you can get is either an "average fineness" for the type, or a "fineness range" of known examples.

Measuring the fineness is not something usually placed as a high priority of analysis for archaeologists (compared to other statistics such as weight, design, and date of issue), especially since until the mid-20th century the only way to obtain an accurate fineness measurement was destructive chemical analysis.

In addition, there's very very little surviving evidence as to what the intended or "official" fineness of the coins was supposed to be. There might be some mention of early Imperial standards, and of course there's the "XXI" fineness mark directly stamped onto coins of Aurelian's coinage reforms, but that's about it. There are no surviving pronouncements of silver debasement; the overall attitude seems to have been "let's gradually dilute the silver and hope nobody notices". Of course, people noticed.

So, the only way to know for sure the fineness of your specific coin is to measure it directly. I'm not entirely sure the Sigma machine is all that reliable for ancient silver, due to metal crystallization and due to the unknown nature of the alloying agents. An XRF would provide a more reliable answer, but of course is much more expensive.

threefifty

You could do a home specific gravity test and pair it with an XRF reading (some coin shops have one and will let you test a coin if you ask nicely). I agree that a Sigma is not useful here as it is consists of a metal detector and is best suited for modern uniform bullion coins.