Commodus copper sestertius

[HELEN S]

 I am moving some coins about and also making sure I have a photo of each one in my collection. I have come across a Commodus which doesn't seem to have a photo, it is a sestertius RIC 312 with Providentia reverse. It is 31mm and weighs 21.03gms. The strange thing is that it has red clearly visible around the edges so does this mean it is made from a copper alloy. Is this usual or unusual. Thankyou for any help.

[curtislclay]

Helen,

Have you compared the color with other unpatinated asses and sestertii/dupondii in your collection that distinctly show red copper on the one hand and yellow orichalcum on the other?

I have often been deceived myself when trying to decide the metal color without comparison!

[HELEN S]

Helen,

Have you compared the color with other unpatinated asses and sestertii/dupondii in your collection that distinctly show red copper on the one hand and yellow orichalcum on the other?

I have often been deceived myself when trying to decide the metal color without comparison!

 Hmmmmmm no I hadn't thought to compare them so I have got for comparison a Faustina AS and a Marcus Aurelius sestertius. Its not as clear cut as you would like to think the Faustina AS is red. The face on Providentia on the reverse of the Commodus coin looks red but just not the red that the Faustina coin looks its duller for want of a word. But it is the edges of the Commoduss coin that look shiny that is what first drew my attention to it. The reverse of the Marcus Aurelius sestertius well the patina seems more solid on this coin and I can only see a peek of colour on victory and this does not look red. After re-looking I would say that there is red showing through on the Commodus coin but tomorrow I will get a second opinion. Is this possible in your opinion?

[curtislclay]

An official, genuine copper sestertius of Commodus would in my opinion be unusual.

According to BMC IV (1940), p. xvii, based on chemical analysis of a small number of specimens, during the Antonine period "the colour of sestertii and dupondii tends to be yellow or brownish yellow when unpatinated, that of the As reddish, but exceptions are not infrequent. Zinc is now present in some quantities in the As, whilst reduced in quantity in sestertius and dupondius. There is in fact no serious difference in composition between the three denominations."

My own experience has been quite different, however: I have observed a distinct color difference between asses on the one hand and sestertii and dupondii on the other right down to the end of the production of those denominations under Gallienus.  A large number of analyses of sestertii and dupondii in the Garonne hoard, published in 1984, showed a drop from about 20% zinc under the Julio-Claudians and Galba and Vespasian to c. 11-14% under Antoninus Pius where the hoard stopped, but that 11-14% under Antoninus was consistent and sufficed to make the coins look yellow. There were no asses in the hoard, just sestertii and dupondii.

For color comparison it would be important to find pieces with large areas of bare metal, not just spots here and there.

[HELEN S]

 Thank you for your valuable opinion the only thing I have found is on the portable antiquity scheme and I have copied a small section of the write up
  Unique ID: BH-34FCB7

Object type certainty: Certain
 Workflow status: Awaiting validation Find waiting to be validated


A copper-alloy sestertius of Commodus, dating to the period AD 180-192 (Reece period 9). Uncertain reverse. Mint of Rome.

Dimensions: 28.4mm diameter, 3.8mm thick. Weight: 17.18g

 I will get another opinion on the colouration tomorrow and try and get some photos thank you again for your time and expertise

[curtislclay]

Helen,

By "copper-alloy" I don't think they were meaning to exclude orichalcum/brass. That too is a copper alloy!

I think they meant what numismatists often call "bronze", i.e. "base metal with large percentage of copper, not gold or silver". They were not trying to specify the composition of the "bronze".