Based on the combination of a Shimano Tourney TY-22 rear derailleur, in combination with the serial number, it's probably a 1996 model or a 1997 model manufactured in 1996. The TY-22 was introduced in mid-1995 for the 1996 model year, according to my Shimano documentation. I do have 1996 Canadian specs listing a Rockhopper 24 with a TY-22.