Right, like marking a shot that's close to the line, I'd assume those are the two 9.9s.  Looks like he's having no problem as is, but as far as "as issued" goes, one is also allowed to make thicker blades, they just have to be the same contour as the original.  Mine are .080" thick and a bit taller as I shoot lighter bullets at higher velocity.  The 1898 rifle sights I use have a V notch cut into them too.  I think there were also Army regulations that allowed some personal modification.  Most likely for target shooters.