All Phenom x2 & x3 processors are quad core with 1 or 2 cores locked. When I got my 550BE and unlocked it I did alot of research as to the chances of unlocking and though many people said it was around 50/50 anyone with real numbers suggested 80-90% on the Dual cores Tri cores its lower. I don't think the date stamps or any other numbers give any indication at all. At the end of the day its a risk so don't try it unless you can live with a dual. Also I think all 555s are C3 not like my 550 which is C2.