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Author Topic: Is this severus alexander denarius authentic? Lustre I've never seen before  (Read 1004 times)

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Offline iameatingjam

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The coin is actually very attractive, and at first I had never suspected it. But thought I'd check in with some of the experts here, see what you guys think on the coins authenticity. I ask because I've never seen a denarius with the same kind of lustre as this one. Again, it looks quite good, I'm just wondering... is it too good?

Its 3g and ~18mm. the price was.. rather expensive. It came from Vcoins from a... somewhat respectable but not foolproof vendor. The edges look pretty normal to me.


Offline mix_val

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That is a nice coin.  Not sure why you suspect it
Bob Crutchley
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Offline Callimachus

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Quote: "I ask because I've never seen a denarius with the same kind of lustre as this one. Again, it looks quite good, I'm just wondering... is it too good?"


The silver coinage of the Empire was on its last legs, and people hoarded it, thinking (correctly) that the coinage that followed would be more debased that the current coinage. Thus the coins of Severus Alexander, Gordian I, II, III, Philip I, II, etc. are often found in EF condition with lustre.

Offline djmacdo

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I would not call that surface luster, but rather slightly etched by corrosion and cleaned.  Still, a very nice coin.

Offline Hydatius

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The silver coinage of the Empire was on its last legs, and people hoarded it, thinking (correctly) that the coinage that followed would be more debased that the current coinage

Well, the silver coinage of the third century was on its last legs, you mean. Diocletian reintroduced a pure silver coinage and it remained in production (even if at low levels) right through into the end of the western empire, although in large numbers only at the end of the fourth. But virtually no 'silver' coinage of the third century was really silver. Both denarii and antoniniani were at or below 50% from the very beginning. So I doubt anybody was hoarding them for their silver content contemporaneously, especially since at least until the time of Cassius Dio the value of the aureus remained at 25 denarii, regardless of the low intrinsic silver value of the 'silver' coinage. But certainly older coinage with a higher silver content would have been pulled from circulation to be melted down for the silver (Gresham's Law). How much 'lustre' such circulated coins would have had is debatable.
Richard
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Offline Ron C2

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But virtually no 'silver' coinage of the third century was really silver. Both denarii and antoniniani were at or below 50% from the very beginning.



This chart has done the rounds on the internet for a couple years now, and is based on lab testing actual coins.  Between 193 and 235, the emperors steadily debased the denarius from a standard of 78.5% to 50% fine or less from 241 onward. 

So in essence, for at least 1/3rd of the third century, the coins were over half silver and generally are not thought of as billon.  From 241 until about 274, many coins still test above 50%, and it appears the official "target" for the mints was around 48%, though from about midway through the Gallienus' reign, you can see this standard trailing off quickly from year to year. Until you start seeing coins with obvious copper content under gallienus, many numismatists still refer to these coins as silver, not billon - though there seems to be a lack of real consensus on where silver ends and billon begins.  These coins in the roughly half-silver range still visually preset as silver and tarnish like silver.  In some cases, you see pebbly surfaces where copper corroded out of the fabric matrix - this is called selective phase corrosion in chemistry circles.
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Offline Hydatius

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So this is the 'show your work' portion of the exam, eh? I was making a general comment in an internet discussion group, so I wasn't going to go into the details, but if you want them, here a bunch of pages from a course booklet I use for upper-year BA and MA courses. Note that the charts treat denarii—which were struck in lower and lower quantities from the reintroduction of the antoninianus until it was phased out as a general production coin by Decius—and antoniniani separately. On the basis of these charts I'll stand by my generalizing comments and add that I find it unlikely that ordinary people would have noticed the difference between a denarius with 45% silver and one with 55% silver. I won't here get into the many problems with Walker's XRF surface analyses, which are only now being slowly replaced (Robin's thesis can easily be found with a Google search). None of this, of course, means that your observations are necessarily incorrect, it's just that there may be a different mechanism behind them from what you think.

Richard
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Offline Ron C2

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Honestly, I didn't post to pick a fight, and I think your reply is great! :)

I do find it odd, though, that there is not broadly accepted convention as to what is billon vs a silver coin.  Billon seems to be a generic term that SOME people would use for anything under 80% purity, while others would consider any statistically significant silver content at all to make a coin billon.  Many (if not most?) dealers, for example, will call a 20:1 antoninianus a billon coin for lack of consensus to the contrary.

In the end, perhaps calling any coin that looks silver - a silver coin - is not really "wrong".

As for selective phase corrosion creating frosted surfaces, I would suggest this can be seen as far back as some late Flavian coins.  Unscientifically, I'm guessing something around 75% or less silver content makes this kind of corrosion more likely if the soil conditions are right.
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Offline iameatingjam

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Thanks for all the input. I think hoarding is a reasonable explanation for the high grade.

 

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