got a new KHS frame under warranty replacement, a XC604. the old frame had, as part ofthe serial # I guess, XC604M stamped in the BB housing but it was marked as a XC104 model. now, the replacement, marked as a 604 model, has XC104M stamped in it. would this be common? dunno if such replacements are based on the model of frame or anything relating to the serial #