Read and write property determining the type of identifier this object uses. Possible values for this property are 0 - nitNumeric: Identifier is a number (LONG), 1 - nitString: Identifier is a String, 2 - nitGUID: Identifier is a GUID-type (Globally Unique Identifier) String, or 3 - nitOpaque: Identifier is an array of bytes. Whenever this property changes, the identifier value is forced to Null.