As far as INFI vs A2 goes, the way I look at it is with handle slabs. I believe when the transition from A2 to INFI happened and it was before tubes came in the picture. Smooth handle means that there is a higher chance that your SHII is A2, and a possibility of INFI. Partially grooved handles is the opposite. These knives are most likely INFI with a very slim chance of A2, fully grooved handles regardless of slots or not is INFI. Maybe 1/10 of 1% that it is A2. This is what I believe to be correct. So initially I look at the handle more than anything.