Strange dmg on Summit Axe 7 - 20

I was hanging around in Borlis Pass with my lvl 20 warrior yesterday when a random lvl 11 necro asked me to help him with the mission. Off we went and somewhere in the middle of it, a gold summit axe dropped for him. He identified it and it appeared to be

Sundering Summit Axe of Defense
Slashing damage 7-20
Armor Penetration 20% (chance 20%)
Armor + 5

He didn’t know the value of it and said it's not max dmg so it probably sucks
I explained him that if he manages to get the sundering mod out he will get rich
We tried (i gave him my sup salvage kit) and he was lucky to get it out!

But what really surprised me is that the base dmg of it was 7. Have you seen axes be 7 instead of 6?

Nothing special. You cant get a 7-28 axe, though.

7-20 (7-19 and 7-21 have been spotted, too) are quite rare, but not unheard of. I got a white 7-20 battlepick off an ettin a few months back.