A Troy pennyweight of 24 Troy grains historically derived from the half of an Islamic pre-existing bullion dirhem of 48 grains. Developing that study of weight standards by a further study of coin weight, Skinner (1967) judged the derivation beyond doubt, after showing the early post reform Arabic dirhem “set the standard for the English Penny Sterling” (i.e. that the 22.5 grain sterling penny is intentionally a half of the 45 grain dirhem), which therefore “had a direct effect upon later English standards”.
Facts concerning the Origin of the Troy Weight Standard – Robert Tye
BNS Research Blog 
You ask: “if anyone still cares about such things?” I do, but I don’t know why. Let us just say that I care about such things because I care about such things. — George Reynolds, Little Elm, TX, USA
Interesting read – thank you. Didn’t Grierson suggest that the Islamic world was the principal conservator of Roman monetary metrology?
Hello George, Rich
Many thanks for the replies. What Grierson really thought seems to me strangely enigmatic. I am curious to get a citation for the point you make Rich. My own general understanding rests fundamentally on two publications from the 1960’s. Skinner’s 1967 take on Offa and Harun in 793, and Grierson’s explanation of what Charlemagne really did in 793 (“Money and Coinage under Charlemagne” 1965). I judge Skinner explicitly revealed the correct underlying 16:15 relationship connecting English and Islamic metrology. Meanwhile Grierson explicitly revealed the correct 16: 15 relationship underlying English and Carolingian metrology. All I am doing at root is saying all three are connected – by that shared understanding. I met Philip Grierson late in 2005, and my key question for him was, why did he never link his own work to Skinner’s? A charming man, he had wished to take me out for a pizza – but I came too late. We chatted generally for a couple of hours in his room, but he apologised – at 95 he was too old for detailed metrological work. He was moved to a care home days later and died a few weeks after that.
I do not have the 1965 Grierson paper to hand, but I recall he gave a correct weight of Charlemagne’s penny (c. 1.7g) and makes 240 of them c. 408g. He then makes that a coin weight, being 15/16 of Charlemagne’s bullion weight of c. 435g. What he must have known but did not say was that Charlemagne’s penny was half an imperial Roman denarius. Also c. 408g is 15 Roman ounces. And c. 435g is 16 Roman ounces. Why did he not just say that?
Going back to your own point Rich, I judge the crucial matter ought to be – where did the Paris grain come from? The later medieval French pound became 18 Roman ounces, but the grain is the one fixed point, at metrification, that was still inherited from Charlemagne. c. 1.7g/32 = c. 0.0531g. Now in his ‘Abd al-Malik paper Grierson postulated what he called a traditional ancient Syrian carat of c. 0.213g. Mathematically that is four Paris grains. From Germany in 2018 Harald Witthöft gave the explicit view that the Paris grain was intentionally a quarter of that “Syrian” carat. In 2022 told me he “got the understanding from Grierson”. Did he mean he got it mathematically from Grierson’s carat, or that Grierson himself thought the Paris grain was also used in the Islamic system? That I cannot say for sure, hence my question to you. Witthöft was then 92, and he died a few months later. Myself, I am sure both Paris and Troy gains came from Islam, and were both part of one greater system created around 697 AD
Enough numbers for now. If this all sounds complicated, well it is not really. The trick is to ignore the distractions. Sadly Wikipedia on “Troy Weight” never mentions Skinner, and if you google Charlemagne’s weight standards, (and its bot) – they will try divert you attention to Harry Miskimin’s work at Yale. John Munro was Miskimin’s Phd student at Yale around 1962. In 1998 in “A Maze of Medieval Monetary Metrology” John revealed what he had already know for 36 years. Miskimin’s ideas about Charlemagne’s weights were complete nonsense. He had waited until both Cipolla and Miskimin were dead before making the matter public. But John Munro died himself back in 2013.
I think all these problems are now solvable – but involve many trips to the graveyard. I do not recall having an informed and thoughtful discussion on these things since I met with Stewart Lyon, who died soon after, in 2021…….
Ha! Seems I woke up in a gloomy mood this morning
All the Best
Rob
Profile fixed?