Dirhem Weight
.
This article is incomplete at present, I plan to add further sections.........
.The classic Islamic dirhem, the reformed dirhem of ‘Abd al Malik, was created around 700 AD. Its creation proved to be a crucial moment in both the history of coinage and of civilization, apparently with repercussions far beyond the caliphate on the economies of Europe and India. Yet during the later 20th century professional scholarship led us into a situation of complete confusion concerning the weight of that dirhem.
Evidence from the coins themselves suggests that the reformed dirhem was intended to weigh close to 2.92 grams. That weight is very close to our modern weight of two sterling pennies – 2.916g. Understanding this fact is one of the clues which lead us to a very surprising insight, the understanding that troy weight is, as our medieval forefathers believed, very ancient indeed, seeming to pre-date even the pyramids of Egypt.
Why do I believe most modern scholars got things so wrong? In my opinion it was in part a result of the nature of modern professional scholarship itself, its over specialization, its remoteness from practical matters, and its tendency towards excessive respect towards ‘established authorities’. More worryingly, it might indicate a willingness to reject the hard evidence in favour of the pre-conceived expectations of peers and the prospective audience.
But first let me now explain the details of this matter, enquiring firstly into what we mean, in practice, when we talk about the weight of an issue of coins, and secondly into how an impractical failure to understand this matter has led to numerous errors.
The Weight of a Coin Issue
Let us first consider the one pound coin currently issued in the UK, specifications at:
http://www.coinauthentication.co.uk/poundfiles.html
We find the weight of the pound coin specified as 9.50g. But what does it mean to say this? It certainly does not, and cannot, mean that every pound coin weighs 9.50000000000000000000.........g
In fact, it specifically means that the average weight of the coins in a batch of more than 106 pieces should be between 9.45g and 9.55g (± 0.05g [ie an average per coin per kilogram])
It also means no individual coin should weigh less than 9.262g, nor more than 9.7368g
(± 0.238g [individual coin tolerance])
So today the weight of an idealised coin in an issue actually seems to be the mid point of two tolerance ranges, a narrow one for the average on bulk weighing, and a broader one for any individual coin. It will be assumed henceforward that in practice coin weight meant something very similar in ancient and medieval mints as it does in the UK today, as we have no direct evidence to the contrary, and the circumstantial evidence all points that way.
There is another weight to bring into consideration in earlier times, when we are dealing with coins which have an intrinsic value based upon their precious metal content. Consider the gold sovereign, specifications at
http://www.coinauthentication.co.uk/geor3circul.html
Its weight was set at 123.274 grains, that is 7.988021g. Its average weight on 47 or more pieces was allowed to vary by ± 0.0166 gram per piece. But a new, much lower, limit was also introduced by legislation “English law allows a sovereign to be legal tender so long as it weighs 122.5 grains, or more; and the difference between this and the full standard weight, or 0.774 grain, represents the margin allowed for abrasion”.
(Jervons http://www.econlib.org/library/YPDBooks/Jevons/jvnMME13.html)
This further weight is a legal one, which applies not to the technicalities of mint practice, but to the legal weight of the coin in circulation. And it is this weight which most concerns the public and is most widely known, since 122.5 grains is the weight standard of the weights supplied to the public for checking the validity of coin that came their way. For a selection of such weights see:
http://www.simmonsgallery.co.uk/2001site/weights/MB47/4701-SovereignWeights.htm
To this set we should add one final weight. That is the weight of bullion that a coin would purchase.
There is an understandable but naive expectation in the population at large that a pound in value, of say silver, ought physically weigh a pound. Libertarians sometimes call for a “return” to such a state of affairs, and many more seem to believe that in some previous golden age, perhaps under the Anglo-Saxons, such was the case. Free coinage of metal (primarily gold), free of seigniorage, was in fact legally enforced in England from 1666 to 1925. Rather ironically the costs of providing this service to commerce were born by state taxation. Prior to 1666 a seigniorage was levied, such that coin exchanged for a higher weight of bullion at the mint. We have clear accounts showing that under Akbar a tola of silver weighed 12 mashas (= 12 grams), whilst the silver rupee weighed 11.5 mashas (11.5 grams). Direct evidence is lacking for many earlier medieval events, but indirect evidence suggests that a sterling penny of 22.5 grains was associated with a troy pennyweight of bullion of 24 grains. Likewise, that under the early caliphs, a coin dirhem of 45 grains was associated with a bullion dirhem of 48 grains
To sum up then, associated with an issue of coin we are liable to have at least seven associated weights,
viz:
1) the idealised weight of the coin
2) & 3) upper and lower boundaries for bulk weighings
4) & 5) upper and lower boundaries for any individual coin leaving the mint
6) a lower boundary for any coin to legally pass as current
7) the weight of the bullion which the coin equalled in value
Evidence from the coins themselves suggests that the reformed dirhem was intended to weigh close to 2.92 grams. That weight is very close to our modern weight of two sterling pennies – 2.916g. Understanding this fact is one of the clues which lead us to a very surprising insight, the understanding that troy weight is, as our medieval forefathers believed, very ancient indeed, seeming to pre-date even the pyramids of Egypt.
Why do I believe most modern scholars got things so wrong? In my opinion it was in part a result of the nature of modern professional scholarship itself, its over specialization, its remoteness from practical matters, and its tendency towards excessive respect towards ‘established authorities’. More worryingly, it might indicate a willingness to reject the hard evidence in favour of the pre-conceived expectations of peers and the prospective audience.
But first let me now explain the details of this matter, enquiring firstly into what we mean, in practice, when we talk about the weight of an issue of coins, and secondly into how an impractical failure to understand this matter has led to numerous errors.
The Weight of a Coin Issue
Let us first consider the one pound coin currently issued in the UK, specifications at:
http://www.coinauthentication.co.uk/poundfiles.html
We find the weight of the pound coin specified as 9.50g. But what does it mean to say this? It certainly does not, and cannot, mean that every pound coin weighs 9.50000000000000000000.........g
In fact, it specifically means that the average weight of the coins in a batch of more than 106 pieces should be between 9.45g and 9.55g (± 0.05g [ie an average per coin per kilogram])
It also means no individual coin should weigh less than 9.262g, nor more than 9.7368g
(± 0.238g [individual coin tolerance])
So today the weight of an idealised coin in an issue actually seems to be the mid point of two tolerance ranges, a narrow one for the average on bulk weighing, and a broader one for any individual coin. It will be assumed henceforward that in practice coin weight meant something very similar in ancient and medieval mints as it does in the UK today, as we have no direct evidence to the contrary, and the circumstantial evidence all points that way.
There is another weight to bring into consideration in earlier times, when we are dealing with coins which have an intrinsic value based upon their precious metal content. Consider the gold sovereign, specifications at
http://www.coinauthentication.co.uk/geor3circul.html
Its weight was set at 123.274 grains, that is 7.988021g. Its average weight on 47 or more pieces was allowed to vary by ± 0.0166 gram per piece. But a new, much lower, limit was also introduced by legislation “English law allows a sovereign to be legal tender so long as it weighs 122.5 grains, or more; and the difference between this and the full standard weight, or 0.774 grain, represents the margin allowed for abrasion”.
(Jervons http://www.econlib.org/library/YPDBooks/Jevons/jvnMME13.html)
This further weight is a legal one, which applies not to the technicalities of mint practice, but to the legal weight of the coin in circulation. And it is this weight which most concerns the public and is most widely known, since 122.5 grains is the weight standard of the weights supplied to the public for checking the validity of coin that came their way. For a selection of such weights see:
http://www.simmonsgallery.co.uk/2001site/weights/MB47/4701-SovereignWeights.htm
To this set we should add one final weight. That is the weight of bullion that a coin would purchase.
There is an understandable but naive expectation in the population at large that a pound in value, of say silver, ought physically weigh a pound. Libertarians sometimes call for a “return” to such a state of affairs, and many more seem to believe that in some previous golden age, perhaps under the Anglo-Saxons, such was the case. Free coinage of metal (primarily gold), free of seigniorage, was in fact legally enforced in England from 1666 to 1925. Rather ironically the costs of providing this service to commerce were born by state taxation. Prior to 1666 a seigniorage was levied, such that coin exchanged for a higher weight of bullion at the mint. We have clear accounts showing that under Akbar a tola of silver weighed 12 mashas (= 12 grams), whilst the silver rupee weighed 11.5 mashas (11.5 grams). Direct evidence is lacking for many earlier medieval events, but indirect evidence suggests that a sterling penny of 22.5 grains was associated with a troy pennyweight of bullion of 24 grains. Likewise, that under the early caliphs, a coin dirhem of 45 grains was associated with a bullion dirhem of 48 grains
To sum up then, associated with an issue of coin we are liable to have at least seven associated weights,
viz:
1) the idealised weight of the coin
2) & 3) upper and lower boundaries for bulk weighings
4) & 5) upper and lower boundaries for any individual coin leaving the mint
6) a lower boundary for any coin to legally pass as current
7) the weight of the bullion which the coin equalled in value
Rob Tye
