Long time ago, I did a glitch to duplicate Dawnbreaker so I got two from the quest. I think this is a commonly known glitch...

Recently, I decided to fix the 'stolen tags' on all my artifacts by dropping them in the basemant of my Hearthfire House and then telling my follower to pick them all up. I then took them from my follower, and the tags were removed! However, when I return back to my basemant I found another Dawnbreaker and another Konahrik Mask. I also seemed to have found an extra Sunhallowed Arrow....

Can anybody explain this to me?