Why Would an Emperor Strike Solidi of Differing Purity?

[John Conduitt]

Is there a reason why an emperor would issue solidi of different purity at the same time?

Take these two issues of Magnus Maximus solidi. Valentinian I’s reform of 367 meant that the gold for solidi was purified to more than 99%, but one of these is less pure - roughly the standard before Valentinian's reform (95%). It's not as if this was a secret debasement to trick the recipients - the purer issue is marked 'OB' for pure gold and the other one isn't. It's also not that Maxumus invented the TROB mintmark to demonstrate the purity of his coins - Gratian had already used both of these mintmarks. Presumably it has nothing to do with the Comitatus mint issuing them, as Maximus was in Trier the whole time.

Coins of this type have been found to contain 94% gold:


Coins of this type have been found to contain 99% gold:

Both photos from the British Museum.

Whether they were issued at the same time is not known, but at Trier they were both very substantial issues struck between 384-387. Perhaps 1m coins of each. That doesn't suggest he struck one for a while and then switched to the other when everyone complained about the purity. So why the difference? Were they for different recipients or different purposes - army vs aristocracy, or special ceremonial issues vs paying barbarians for their cooperation? Or something else?

[traveler]

Maybe because the solidus with TROB mintmark is meant to convey unity and equality with Theodosius I in the East. Theodosius I was striking solidi with the CONOB mintmark.

[Curtis JJ]

Without looking into this particular issue or period, I do think the different recipients explanation is the likeliest. I can't recall off the top of my head, but there are other cases of producing coins of different purity for internal use and for export. (Will edit in examples if I can find/remember any specifics.)

I also wonder if it's possible that if the gold was from different sources (e.g., spoils from a campaign or tribute from a client kingdom or whatever), it may not have been worth it to refine out an additional few percent of AR/AE/PB/etc.

Edited January 24 by Curtis JJ

[John Conduitt]

8 hours ago, traveler said:

Maybe because the solidus with TROB mintmark is meant to convey unity and equality with Theodosius I in the East. Theodosius I was striking solidi with the CONOB mintmark.

Yes this makes sense in terms of why that reverse is on the OB coin. The VICTORIA AVGG reverse is always an OB or COM coin, except a few early ones from Valentinian I and Valens.

[John Conduitt]

8 hours ago, Curtis JJ said:

Without looking into this particular issue or period, I do think the different recipients explanation is the likeliest. I can't recall off the top of my head, but there are other cases of producing coins of different purity for internal use and for export. (Will edit in examples if I can find/remember any specifics.)

I also wonder if it's possible that if the gold was from different sources (e.g., spoils from a campaign or tribute from a client kingdom or whatever), it may not have been worth it to refine out an additional few percent of AR/AE/PB/etc.

I can't think of a better explanation. I wondered whether the purer issues were for his soldiers, who didn't like being short-changed, and where you'd likely get the coins back again in taxes. The lower quality gold was for export. You'd want to price in a 5% discount for the risk, and for the fact that you might not get it back when gold was in short supply. Then, as you say, whatever gold you get from abroad is probably less pure, and you just melt it down and send it back out again.

[Magnus Maximus]

Fascinating subject, and one that I wasn't previously familiar with. It raises a question: Could the reduction in weight of siliquae in the Italian mints under Maximus's control also be connected? If my memory serves me right, he decreased their weights by approximately 30%, while maintaining their purity, and these circulated alongside the "heavier" issues still being produced at Trier.

[John Conduitt]

5 hours ago, Magnus Maximus said:

Fascinating subject, and one that I wasn't previously familiar with. It raises a question: Could the reduction in weight of siliquae in the Italian mints under Maximus's control also be connected? If my memory serves me right, he decreased their weights by approximately 30%, while maintaining their purity, and these circulated alongside the "heavier" issues still being produced at Trier.

It is odd that the weight was reduced, even if the Italian coins came after the Trier coins. Valentinian II seems to have struck heavier coins at the same mints before like RIC 27A and afterwards like RIC 43C, but also lighter ones like RIC 14A. They can't have fooled anyone, so it must be a different denomination and/or for a different recipient.

Edited January 30 by John Conduitt

[Magnus Maximus]

2 hours ago, John Conduitt said:

It is odd that the weight was reduced, even if the Italian coins came after the Trier coins. Valentinian II seems to have struck heavier coins at the same mints before like RIC 27A and afterwards like RIC 43C, but also lighter ones like RIC 14A. They can't have fooled anyone, so it must be a different denomination and/or for a different recipient.

What's particularly odd is the discovery of siliquae of various weights in large hoards, grouped together. This has led some historians, including one I've heard, to suggest that siliquae were valued and circulated more for their bullion weight than as a distinct coin denomination. This theory seems plausible to me, and I tend to agree with it.

[John Conduitt]

10 hours ago, Magnus Maximus said:

What's particularly odd is the discovery of siliquae of various weights in large hoards, grouped together. This has led some historians, including one I've heard, to suggest that siliquae were valued and circulated more for their bullion weight than as a distinct coin denomination. This theory seems plausible to me, and I tend to agree with it.

There is, of course, the question of who was doing the hoarding and whether they were the same people for whom the coins were struck. A lot of the British hoards might be Saxon loot, or even payments from the Romano-British to Saxon mercaneries. The Saxons would most likely have used them as bullion.