Actually my hd595 drivers haven't got the HD 555 595 and Sys, just a date (29.01.07 if I remember correctly). I just thought this is quite funny actually and possibly indicates something (or maybe not).
I was quite surprise to see that HD280 driver that has "HD555/595" written on it..
It's different from my HD555's drivers..
this is the close-up snapshot from the left driver of my HD555: