Is this Denarius of Claudius (VIIII IMP – SPQR PP OB CS) fake?

[Nick C3]

Determination: Claudius, AR18 – 3,6g, Denarius, Rome, ‘VIIII IMP – SPQR PP OB CS’, 46-47 (RIC ??, unknown with VIIII)

Metal composition: 74% silver, 25% copper.

[John H8]

I could be wrong here but weren’t denarii from this period 95-98% silver?

There’s probably some variation, but from what I’ve read they kept it pretty close to that range. I’m sure someone with a lot more knowledge than me will chime in though.

[SRukke]

Looks like a die match to several of the fakes in the reports.

 

[PMah]

That's pretty amazing that you would do a metal composition test, potentially destructive, on a coin that would be quite valuable if it was real, without an understanding of the metalurgy, prior to doing a simple die study against known fakes.

[John H8]

Whenever I bring a coin in to my local dealer he just uses an XRF gun to analyze the composition of the coin. I am assuming this is what op meant? I think it’s not destructive or damaging to the coin, or is that incorrect?

[Hydatius]

XRF is almost completely useless as a test for silver and bronze coins since it only measures the surface of a coin and silver and copper oxidize. And for the test to be done properly, the XRF device needs to be properly calibrated for the material being analysed.

Richard

[Nick C3]

That's pretty amazing that you would do a metal composition test, potentially destructive, on a coin that would be quite valuable if it was real, without an understanding of the metalurgy, prior to doing a simple die study against known fakes.

It's just a 10 seconds test with a spectrometre.

[Nick C3]

XRF is almost completely useless as a test for silver and bronze coins since it only measures the surface of a coin and silver and copper oxidize. And for the test to be done properly, the XRF device needs to be properly calibrated for the material being analysed.

Richard

That's totally incorrect Richard. It measures all of the metal, not only the surface. My wife works with an XRF-device and knows what sh'e doing

[traveler]

I'm sorry Nick but Richard is right and you are mistaken. Maybe you'd like to check with your wife again?

There's literally a whole book written on how to overcome the surface limitations of XRF.

[Hydatius]

That's totally incorrect Richard. It measures all of the metal, not only the surface. My wife works with an XRF-device and knows what sh'e doing
[/quote]

Ah, I hate to pull rank on you, but one of my graduate students wrote an MA thesis basically demolishing all of David' Walker's widely-quoted XRF analyses on silver and I have co-written two articles on the subject in the Journal of Analytical Atomic Spectrometry (DOI: 10.1039/c4ja00170b and DOI: 10.1039/c8ja00227d). I'd attach them here but the site doesn't take PDFs.

So, no, XRF does not measure anything below the surface of an object.

Richard

[Nick C3]

Sorry guys, I'm totally wrong indeed, I didn't listened well enough to her

[Nick C3]

So, conclusion is that this coin is fake or ... ?

[Jay GT4]

100%

[John H8]

That's totally incorrect Richard. It measures all of the metal, not only the surface. My wife works with an XRF-device and knows what sh'e doing

Ah, I hate to pull rank on you, but one of my graduate students wrote an MA thesis basically demolishing all of David' Walker's widely-quoted XRF analyses on silver and I have co-written two articles on the subject in the Journal of Analytical Atomic Spectrometry (DOI: 10.1039/c4ja00170b and DOI: 10.1039/c8ja00227d). I'd attach them here but the site doesn't take PDFs.

So, no, XRF does not measure anything below the surface of an object.

Richard
[/quote]

That’s very interesting, so it measures only the outer layer, you’d think the tech would be there in todays day and age to analyze a coin through and through. Does the article discuss just how deep it actually penetrates? Just curious. I thought about specializing in radiology initially , I didn’t in the end, but I always found it very interesting, even beyond just what is pertinent to surgery.

So do you feel it is useful AT ALL in helping to determine whether a coin is authentic or not? What would be a better method to analyze the metal content? Is there a feasible alternative that wouldn’t destroy the coin? Also how often do fakes have an accurate replication of the composition of the coin it is imitating? I would have to think XRF would have some value in helping to determine authenticity, if nothing else to send up red flags if the composition is totally off from what it should be, even if it is just measuring the surface layer, but I suppose there would be other red flags in such a coin, and the analysis wouldn’t really be needed to determine its authenticity (or lack there of)

[PeterD]

What would be a better method to analyze the metal content? Is there a feasible alternative that wouldn’t destroy the coin? Also how often do fakes have an accurate replication of the composition of the coin it is imitating?

The method used is to drill a hole into the rim of of a coin and analyse the shavings.

If you are interested, find a copy of 'The Metallurgy of Roman Silver Coinage' by Kevin Butcher and Matthew Ponting. This describes the process and the reasons why it is needed as well as the results of the analyses. There are other books and papers by these authors as well.

Obviously it is not feasible to test coins in this way just as a means of checking authenticity. In any case, fakers have been known to use old worn coins as a basis for their fakes.

[Hydatius]

That’s very interesting, so it measures only the outer layer, you’d think the tech would be there in todays day and age to analyze a coin through and through. Does the article discuss just how deep it actually penetrates? Just curious. I thought about specializing in radiology initially , I didn’t in the end, but I always found it very interesting, even beyond just what is pertinent to surgery.

So do you feel it is useful AT ALL in helping to determine whether a coin is authentic or not? What would be a better method to analyze the metal content? Is there a feasible alternative that wouldn’t destroy the coin? Also how often do fakes have an accurate replication of the composition of the coin it is imitating? I would have to think XRF would have some value in helping to determine authenticity, if nothing else to send up red flags if the composition is totally off from what it should be, even if it is just measuring the surface layer, but I suppose there would be other red flags in such a coin, and the analysis wouldn’t really be needed to determine its authenticity (or lack there of)

There are a variety of methods including neutron activation, LA-ICP-MS, PIXE, and LIBS (you can find all sorts of videos on metal analysis like these on YouTube), but the gold standard is what we call 'wet analysis', which involves dissolving a portion of the coin in acid and measuring the metals. Apart from various forms radiation activation methods, the best methods are all destructive.
Richard

[PMah]

Yes, learn what authentic coins look and feel like in hand.  Testing is essentially meaningless by comparison to other criteria, which vary significantly.
   The academic or professional metallurgy studies are and were performed for reasons other than authenticity.   From careful studies, numismatists get a better understanding of economics and related concepts related to the issuing authority.    But the sampled coins were authenticated by traditional means.  A few percentage points of silver, measured across time and samples, statistically adjusted, may be very significant.  But a specimen with a bit of variance off an internet-stated norm is likely meaningless. 
  And, again, the metal content value is "chump change" compared to collector pricing (or fraudster profit margin.).

[jmuona]

Fake, yes.
As to metal analysis, the actually important thing - scientifically - is not the total metal composition of the coin NOW. It can be done without destructive methods (neutron activation analysis), but it will only tell you what the composition is today. It will not tell you what the flan was like when minted, only what it is like today, after having suffered a lot. All ancient coins have changed during the millennia.
The original composition is what an archeologist/historian needs to figure out.

By the way, surface analysis of a Claudius denarius would be just fine (even Walker's measurements, Richard) as they were as pure silver as people were able to get at the time. So you really do not need a better methods for that specific coin. For most later coins you certainly do need something else because of intentional surface silver enrichment by the mint. It certainly is not only a question of surface oxidation.

As to recognizing a fake 1st century Roman coin, well, as people have already told here, a metal analysis is not really the best (or the first) option.

Jyrki Muona