Regarding to get old pension scheme benefits

We r a group of 19 candidates got selected/recruited for post of Lab. Assistant through DSSSB vide o.o. dated 29-10-2003& our Dozier's were sent to Concerned deptt on 06-11-2003. But our Medical examination & police verification took almost a year & our joining took place from July 2004 to October 2004. Are we eligible for old pension as our recruitment process got completed in 2003 & on which ground or rule kindly mention. Department is providing us New pension Scheme saying tat our joining was after 01-01-2004. Is d basis of providing benefits to a candidate considered on basis of date of recruitment or date of actual joining. Kindly provide proper reply ..Thanx