Case 2 Blade Equal end Pen?

[T. Erdelyi]

I recently bought a very old Case equal end pen my question is that one
blade is ground very thin and is very flexible, kind of like a fillet blade. The only other markings are on the master blade and they are AGI
Can anyone tell me why and what this blade was used for. If I can provide
more information email me at terdelyi@epix.net