Method replacesthe tag value if the tag is present in the metadata tree, or null otherwise.

This method accesses the EnvelopePriority DataSet (1:60). The DataSet specifies the envelope handling priority and not the editorial urgency (see 2:10, Urgency). '1' indicates the most urgent, '5' the normal urgency, and '8' the least urgent copy. The numeral '9' indicates a User Defined Priority. The numeral '0' is reserved for future use.

Contains a single byte, consisting of a numeric character.