There were six agoranomoi (market officials) in the fifth century, ten in the first half of the fourth century. Their duties were posted in front of the Agoranomion (Market Officials' House) in the Athenian marketplace. These included supervising: the market area; the conduct of persons circulating in it; and the goods on sale. The agoranomoi also enjoyed certain powers of a judicial nature, such as for instance being able to impose a fine. Lastly, they were responsible for collecting certain taxes, such as:
The 'agoranomic' tax, a tax paid by Athenian traders in order to book a pitch in the Agora (or its arcades) as a sales area.
The 'xenic' tax, paid by foreigners for the use of the marketplace.
The prostitute tax and
the consumption tax, imposed on products bought in the market.

There were ten of these in all: five for the city of Athens and five for the port of the Piraeus. This we know from Aristotle (Ath.Pol. 51.2). They were responsible for traders' proper use of public weights and measures.
An official set of bronze weights bore symbols for particular subdivisions. For example, the stater (about one kilo in weight) bore an astragalos.
The officially appointed measures, like the Athenian coinage, bore the seal of Athena's head and her owl. Liquids were measured in a small jug one kotyle in capacity. Dry goods were measured in cylindrical vessels.