A History of Troy Weight

[EWC]

Hello All,

I have been researching the historical weight standards underlying coin issue for about 30 years. I have become concerned about what seems to be a rapidly decline in understanding of the subject in general.  I joined this group specifically in the hope of informed discussion of the History of Troy weight here.

For starters then – the 1351 gold noble of Edward III is widely quoted as 120 Troy grains

By modern standards that ought to be 7.776g

Actual coins seem to bear this out – for instance this one is stated as 7.75g

https://www.cngcoins.com/Coin.aspx?CoinID=395895

The variation seem to me trivial – well within what we would assume to be the toleration (the “remedy at the shear”). Alternatively, if the Troy weight standard has changed since 1351, it is not by very much.

I therefore conclude that the Troy weight standard already existed in 1351, and was used to regulate coin weight.

I wonder if anyone differs?

Robert Tye

[Diaconis]

I hope that everyone had a most enjoyable Christmas, I certainly did with the concomitant lashings of Christmas comestibles for which I paid for in a regrettable surfeit of calories and post-festive penitence😂..... 

Haven't "been on" for a while and noticed this interesting post by Mr. Tye, so I thought I'd have a stab at it...

On 12/23/2025 at 10:08 AM, EWC said:

Hello All,

I have been researching the historical weight standards underlying coin issue for about 30 years. I have become concerned about what seems to be a rapidly decline in understanding of the subject in general.  I joined this group specifically in the hope of informed discussion of the History of Troy weight here.

For starters then – the 1351 gold noble of Edward III is widely quoted as 120 Troy grains

By modern standards that ought to be 7.776g

Actual coins seem to bear this out – for instance this one is stated as 7.75g

https://www.cngcoins.com/Coin.aspx?CoinID=395895

The variation seem to me trivial – well within what we would assume to be the toleration (the “remedy at the shear”). Alternatively, if the Troy weight standard has changed since 1351, it is not by very much.

I therefore conclude that the Troy weight standard already existed in 1351, and was used to regulate coin weight.

I wonder if anyone differs?

Robert Tye

You are quite right to point out that the observed weights of surviving 1351 nobles cluster very closely around what we would now express as c. 120 Troy grains, and that the variation you cite (for example, 7.75 g) is entirely consistent with normal medieval tolerances, including the remedy at the shear. On purely numerical grounds, the metrology is remarkably stable.

Where I would differ is not on the arithmetic, but on the historical inference drawn from it.

There is no evidence¹ that the Troy weight system as such—that is, explicitly named, formally defined, or administratively adopted—existed in England in 1351 or was used as “Troy” to regulate coin weight. At that date the Tower mint, producing the noble, was still operating explicitly in Tower weight, and continued to do so until its formal replacement by Troy weight in 1527 under Henry VIII. Expressed in Tower-weight terms, a nominal 120 Troy-grain noble corresponds to 112½ Tower grains (120 × 450⁄480), which fits comfortably within contemporary Tower-weight reckoning.

What your figures do demonstrate, however, is that the grain employed in England in 1351 is effectively identical to the later Troy grain, and that the regulation of the noble’s weight is entirely consistent with what we would now describe as Troy-grain-based measurement. In that limited, practical sense, the Tower system behaves exactly as Troy would later behave. In this respect, Tower and Troy weights did not derive from one another but descend from a shared metrological ancestry, which is precisely why the English transition from Tower to Troy in 1527 was arithmetically seamless.

The difficulty, then, is one of nomenclature rather than metrology. To describe the 1351 standard as “Troy” risks importing a sixteenth-century administrative label into a fourteenth-century context. In short, the numbers are sound; what is at issue is whether it is historically accurate to call them “Troy” before the name, the system, and the administrative framework had yet been adopted in England.

¹Should anyone be aware of a fourteenth-century English mint ordinance that actually uses the word “Troy,” I would be delighted to see it; until then, the numbers seem stubbornly unimpressed by nomenclature.

With that, may I wish everyone a very happy New Year. May your grains be stable, your scales honest, your tolerances forgiving, and your anachronisms few — and may 2026 finally deliver that elusive coin we all hope to find. 🥳

 

[secret santa]

All Greek to me, I'm afraid.

[EWC]

On 12/28/2025 at 2:55 PM, Diaconis said:

I hope that everyone had a most enjoyable Christmas, I certainly did with the concomitant lashings of Christmas comestibles for which I paid for in a regrettable surfeit of calories and post-festive penitence😂..... 

Haven't "been on" for a while and noticed this interesting post by Mr. Tye, so I thought I'd have a stab at it...

You are quite right to point out that the observed weights of surviving 1351 nobles cluster very closely around what we would now express as c. 120 Troy grains, and that the variation you cite (for example, 7.75 g) is entirely consistent with normal medieval tolerances, including the remedy at the shear. On purely numerical grounds, the metrology is remarkably stable.

Where I would differ is not on the arithmetic, but on the historical inference drawn from it.

There is no evidence¹ that the Troy weight system as such—that is, explicitly named, formally defined, or administratively adopted—existed in England in 1351 or was used as “Troy” to regulate coin weight. At that date the Tower mint, producing the noble, was still operating explicitly in Tower weight, and continued to do so until its formal replacement by Troy weight in 1527 under Henry VIII. Expressed in Tower-weight terms, a nominal 120 Troy-grain noble corresponds to 112½ Tower grains (120 × 450⁄480), which fits comfortably within contemporary Tower-weight reckoning.

What your figures do demonstrate, however, is that the grain employed in England in 1351 is effectively identical to the later Troy grain, and that the regulation of the noble’s weight is entirely consistent with what we would now describe as Troy-grain-based measurement. In that limited, practical sense, the Tower system behaves exactly as Troy would later behave. In this respect, Tower and Troy weights did not derive from one another but descend from a shared metrological ancestry, which is precisely why the English transition from Tower to Troy in 1527 was arithmetically seamless.

The difficulty, then, is one of nomenclature rather than metrology. To describe the 1351 standard as “Troy” risks importing a sixteenth-century administrative label into a fourteenth-century context. In short, the numbers are sound; what is at issue is whether it is historically accurate to call them “Troy” before the name, the system, and the administrative framework had yet been adopted in England.

¹Should anyone be aware of a fourteenth-century English mint ordinance that actually uses the word “Troy,” I would be delighted to see it; until then, the numbers seem stubbornly unimpressed by nomenclature.

With that, may I wish everyone a very happy New Year. May your grains be stable, your scales honest, your tolerances forgiving, and your anachronisms few — and may 2026 finally deliver that elusive coin we all hope to find. 🥳

 

Dear Diaconis,

Delighted to find we exactly agree regarding observed weights.

D > There is no evidence¹

It looks as though you intended to footnote this claim – is that the case? I would much like to get reference to any published sources you favour backing up your position here.

Broadly, we are at cross purposes. In general you are addressing the use of words, I am addressing the understanding of things. I agree the Troy weight system apparently got that name around the later 14th century, but hold that the system, as we know it, existed long long before that.

Readers should note that there are two later 20th century official English publications on the topic, both HMSO publications from the London Science Museum. Skinner in 1967 tentatively hints that the ultimate origins of Troy weight standards were in Egypt, maybe as early as 4,000 BC. Connor in 1987 tentatively associated them with the metrological reforms of Nero. Meanwhile it is implicit in Grierson (and explicit in both Skinner and Connor) that both standards were a single system already existing in the Anglo-Saxon period.

D > a nominal 120 Troy-grain noble corresponds to 112½ Tower grains (120 × 450⁄480).

To the best of my knowledge there are only two documents even positing the existence of such a “Tower grain”. One is the famous, (or perhaps infamous) “Tractus de Ponderibus” of the early 13th century. In 1987 Connor (p. 125) called that account “simply not true”. The other is a single obscure internal mint document brought to light by Stewart Lyon. From personal discussion with Stewart I know he was later open to the suggestion that that was just an ephemeral 13th century matter.

D > In this respect, Tower and Troy weights did not derive from one another but descend from a shared metrological ancestry.

A tantalising suggestion that maybe we are closer than you otherwise suggest? It seems overwhelmingly probable to me that Tower was merely a coin weight, derived from a Troy bullion standard, by a gross charge on coining, by weight, of 15/16. That such had roots at least in the Anglo Saxon period is explicit in Skinner and Connor, and implied by Grierson. Meanwhile - what “shared metrological ancestry” do you posit?

Finally, I met the delightful Henri Pottier, and corresponded with Elsen, Doyen and de Callatay. Now I get further evidence that metrological study thrives in Belgium 🙂

Meanwhile I get no reply here at all, from anyone in the Britain, concerning this, the foundation stone of our “pre-decimal” coinage. 😞

All the Best for 2026

Rob Tye

[EWC]

Hello Diaconis

On further thought I have doubts about this:

D > a nominal 120 Troy-grain noble corresponds to 112½ Tower grains (120 × 450⁄480).

Tractus de Ponderibus makes the sterling penny 32 rather than 30 grains - so applies a "Tower wheat grain" smaller than the "Troy wheat grain"

Thus I would assume the notional calculation you are reaching for would make a nominal 120 Troy-grain noble correspond to 128 such "Tower Grains" (120 x ⁴⁸⁰/450)

Did I miss something?

Regards

Rob