The Roman town Pompeii was famous for its garum, a type of fish sauce. In one of the shops where it was sold, archaeologists have found a jar marked “kosher garum.” It must have contained garum prepared according to Jewish rules, excluding shellfish and other nonkosher ingredients (Berdowski 2006, p. 249). Obviously, it was labelled because it would otherwise have been difficult to distinguish from a nonkosher garum. In modern terms, being kosher was a credence attribute of the fish sauce. By this is meant that the customer herself could not determine whether the garum had the attribute or not; she would simply have to rely on the merchant.
Today, food labelling is much more common than in the Roman era. One reason for this may be that consumers are now more concerned with credence attributes of food. Another plausible reason is the increasing length of food distribution chains....