First thank you really much for your input it's really appreciated, i'm a bit bummed for the barrel and bolt, I really didn't thought of it that way but now that you say it, it make sense the typo is really not the same on the barrel and the D is a dead give away.
Maybe it's me that want it to a real replacement bolt body too much, but I'm really sure that the 81006 serial is marked on the round part of the bolt handle haha!
So I just call the guy that sold it to me and he said that he scrap two originals top handguards because they were almost completely destroy.
I check the headspace with small disc gauge, it did not close on the field and the no go ones! still I think I will follow your advice and use a string and be far away just to be sure!