Well class, if you are sitting comfortably, I will begin 😀

The avoirdupois system is both an updated modern as well as an historic measurement system of weights (using units such as pounds and ounces) that became commonly used in the 13th century, but was updated (1959) to represent, (by law) mass in line with SI based units.
The rise in use of the measurement system corresponds to the regrowth of trade during the High Middle Ages after the early crusades, when Europe experienced a growth in towns, turned from the chaos of warlordism to long distance trade, and began annual fairs, tournaments and commerce, by land and sea. There are two major hypotheses regarding the origins of the avoirdupois system. The older hypothesis is that it originated in France. A newer hypothesis is that it is based on the weight system of Florence.
The avoirdupois weight system is thought to have come into use in England circa 1300. It was originally used for weighing wool.
From the 14th century until the late 16th century, the systems basis, the avoirdupois pound, the prototype for today’s international pound was also known as the ‘wool pound’ or the avoirdupois wool pound.
The earliest known version of the avoirdupois weight system had the following units: a pound of 6992 grains, a stone of 14 pounds, a woolsack of 26 stone, an ounce of 1⁄16 pound, and finally, the ounce was divided into 16 “parts”.
In England, Henry VII authorized its use as a standard and Queen Elizabeth I acted three times to ensure a common standard establishing what became the Imperial system of weights and measures. Late in the 19th century various governments acted to redefine their base standards on a scientific basis and establish ratio-metric equations to SI metric system standards. They did not always pick the same equivalencies, though the pound remained very similar; these independent legal actions lead to slight (small fractional) differences in certain quantities, such as the American and Imperial pounds, et al.
In 1959 by international agreement, the definition of such pound and ounce units became standardized among countries using the pound-based mass units. The International Avoirdupois Pound so created is the everyday system of weight used in the United States and is still used to varying degrees in everyday life in the United Kingdom, Canada and some other former British colonies despite the official adoption of the metric system.
info from Wiki

These were my Mum’s weighing scales, and we still use them today 🙂