A more thorough explanation:

Definition: An assizer is a person who has different roles in different contexts. In history, an assizer was a member of a grand assize. In Scots law, an assizer was a juror. In the context of weights and measures, an assizer was a person who had custody of the standards of weight and measure and fixed the assize of bread, ale, and other items of general consumption. The term can also be spelled as assizor, assiser, or assisor.

• In medieval England, an assizer was a member of a grand assize, which was a group of 12 knights and freeholders who were summoned to determine the right of property in a dispute.
• In Scots law, an assizer was a juror who was responsible for deciding the facts of a case.
• In the context of weights and measures, an assizer was a person who ensured that the standards of weight and measure were accurate and fixed the assize of bread, ale, and other items of general consumption. For example, an assizer might determine the weight of a loaf of bread or the volume of a pint of ale.

These examples illustrate the different roles that an assizer could have depending on the context. In each case, the assizer was responsible for ensuring that justice was served and that standards were maintained.