Go to your Active Listings
At the top of the List there is a box called Item Title.
Add some key words from your duplicates list.
You should get both duplicated listings.
There are check boxes on the left. Check off the listings you want to delete.
Now. Look for the Action dropdown menu. Click on End.
We've all done it. Sometimes eBay catches it and sometimes they don't. And sometimes eBay relists a Sold item. That's MUCH harder to catch.