well, duplicate kalka mail is the name called locally at some places, but still its better to call it hwh ndls bi weekly...dont go for press...they may even call dd as intercity and express as mail...they hardly know any differences betn class of trains...no where is it announced/displayed as duplicate kalka mail...where as hwh ndls bi weekly is the official and more popular name for the origin, destination and some of the intermediates as well...