It is interesting, what armor in the 19th century could be pierced in Afghanistan?
I think hardly anyone will disagree that the dagger in question is dated to the middle (and this is at best) or the late 19th century ... It is enough to examine the old photographs and engravings to make sure that at this time mail armor in Afghanistan was a rarity.
Ordinary Pesh Kabz with a faceted point. Like this: