User:Hans Adler/Tower pound

The tower pound of 12 tower ounces, or the tower mark of 8 tower ounces, was the unit of mass used for the penny coins produced by the English Royal Mint in the Tower of London throughout much of the Middle Ages. The tower pound, mark and ounce were precisely 15/16 of an English troy pound, mark or ounce. The tower ounce was subdivided into 24 tower grains.

The pennyweight of the tower pound was also known as the sterling, defined as one twentieth of a tower ounce. King Offa's money reform around 792 introduced penny coins consisting of a sterling of sterling silver. In a gradual process of debasement starting in 1280, more and more coins were struck to the pound until in 1527 the mass of a sterling penny reached one forty-fifth of a tower ounce (0.44 sterling pennyweights) and the tower pound was officially abolished. (See for details of the debasement. Apparently it was caused by silver shortage.)

The Scottish merchant pound as attested in 1426 had the same mass as the tower pound, but it was divided in 16 derived ounces and combined to a stone of 16 pounds. (Silver coins were often used as weight pieces, and so it is no surprise that the tower pound was used in English and Scottish trade before, and for some time after, debasement made this practice impossible. Such a merchant ounce had a mass of 15 sterling.)

Use in minting, in connection with the French pound, later the troy pound. David's Assize, wheat/barley.

In Offa's time, England traded with the Arabic world. (And in fact some gold dinars were issued in his name.) It appears that his money reform around 792 was based on the Arabic system, the heavier new penny having half the mass of a silver dirham. It also appears that the Arabs had another standard for bullion, which was 16/15 their standard for silver coins. 

Flat silver pennies were introduced in a precursor to the Carolingian money reform, by Charlemagne's father Pepin the Short in 755. They are first attested in England in the coinage of two Anglo-Saxon kings in Kent towards the end of the 8th century CE, which was then taken over by Offa of Mercia. Increase in weight from 19+ troy grains (1.2+ g) to 20+ troy grains (1.3+ g) under Offa. This happened around 792, possibly to make them incompatible with the Frankish coins. Charlemagne in 793/794 increased the penny to 1.7 g. (Charlemagne in 790 threatens Offa in a trade dispute.)

http://www.economics.utoronto.ca/munro5/MONEYLEC.htm (Reason for the reform: Rareness of gold due to Islam. http://www.nbbmuseum.be/2006/11/islam.htm ) http://www.amazon.com/Wealth-Anglo-Saxon-England-Peter-Sawyer/dp/0199253935/ref=sr_1_4?ie=UTF8&qid=1359905623&sr=8-4&keywords=rory+naismith

Weight estimates:

Offa light standard: 1.15-1.30 g. "almost certainly based on the same standard as early Carolingian coins"

Offa heavy standard: 1.30-1.45 g.

Offa's reform to heavier coins probably predated Charlemagne's a little, but not to the same target.

Rory Naismith, Money and Power in Anglo-Saxon England: The Southern English Kingdoms, 757-865, p 174f

Debasement of 840s and later appears based on bullion shortage.

Rory Naismith, Money and Power in Anglo-Saxon England: The Southern English Kingdoms, 757-865, p 180

Mass of post-Charlemagne penny: 1.70 or 1.76 g.

Penny


 * History of the English penny (c. 600 – 1066)
 * Anglo-Saxon pound