It turns out, that it has a lot to do with making process. The head is shaped like this when they put it under forging press to make a nail puller. It happens when the press chisel (don't know the exact word) becomes blunt. Dad said that this was a big problem, as they made loads of heads in one day and they had to sharpen those things all the time. But at the same time it is normal, that the head is facing a bit forward like we see on Dave's and Robin's example. Pic's coming later.