INamedValue2 is an extended interface supported by NamedValue objects in PI-SDK 1.1 and later releases. It contains all methods and properties of NamedValue, as well as these additional methods:
MTNV is a thread-safe version of NamedValue. It implements all the NamedValue and INamedValue2 methods and properties as well as native versions (prefaced by "MT") of the same.
For more information on extended interfaces, click here.