it don't look like duped items for me.
Dupe isn't that easy, and +10 is hard as hell. First he'll have to do +8, really easy for a duper. Then +9. A bit harder, but he'll succeed if he got enough time/luck. But then +10, it'll take so long to dupe a lot of +9, and even with a lot of those (let say 50, which is a LOOOT), maybe he won't be able to get a +10. So now, think about how long it would take for someone to get a full +10 set. (5 part, + his dual wield, which make 7 +10 ).
Imo, this is just gm edited/db hacked.