historically, what was this units purpose?
Many transaction prices were agreed using a quantity of a unit of account.
Unit of account
many transaction prices were agreed using a quantity of a unit of account. 
which unit is used to measure mass in the metric system UNANSWERABLE what is this system? It  is a system of measurement that succeeded the decimalised system based on the metre introduced in France in the 1790s. what are some of its common ones? Mètre des Archives and Kilogramme des Archives what is the emu system? Several systems of electrical units were defined following discovery of Ohm's law in 1824. what are the prefixes used here? In the metric system, multiples and submultiples of units follow a decimal pattern and in the early days, multipliers that were positive powers of ten were given Greek derived prefixes such as kilo and mega and those negative were given centi and milli. what does gravitational system uses? It uses  the kilogram-force (kilopond) as a base unit of force, with mass measured in a unit known as the hyl, "Technische Masseneinheit" (TME), mug or metric slug. what are some of the related units of kilopond? Tonne-force, metric ton-force, megagram-force, and megapond. what are the currency units in the measurement system? Unit of account where is this unit used? It is used to compare against each other; for example, goods, services, assets, liabilities etc and for financial accounting to describe the specific assets and liabilities and historically many transaction prices were agreed using this unit.
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Unit of account [SEP] Introduction
Historically, many transaction prices were agreed using a quantity of a unit of account. The actual payment might include a number of other types of coin, and other goods, agreed to be equivalent in total to the sum agreed.