The blade edge is very thin. Bread-knifing by had would take an inordinate amount of time. The crack extends all the way though and as you run the blade edge across your thumbnail and watch the ripple effect as you move down, you get to this spot and it really shows. The crack goes up and does a curve back toward the rear of the blade.

The blade width from top of spine to cutting edge is 0.674" 5/8 = 0.625" Now if if I get rid of the crack at the very top, the blade will now be about 0.588" width, larger than a 4/8 = 0.500" , but will be under the 5/8 (0.625") by about 0.037" or as it reads at Boeing, where I used to work, 37 thousandth, or 88 thousandth wider than a 4/8 razor. That wold be a shame, since this is a very small spine area that quickly thins to the width of a DE blade most of the way down the blade. If it were not for the flaw, it might be a "singing" blade.?? Possible?