I was wondering how the inventory gets cached and found two files in the cache folder named xxxxxx.inv.gz. The smaller one appears to be the system inventory, the other is all my goodies.
So make a *COPY* of the larger one that contains your inventory items, and put it somewhere safe while you do this to the copy!!!
'tar -xf whateverthelongcodeis.inv.gz' - to turn it into a txt file.
'grep name | sort > inv1.txt' - to strip out all the named items into inv1.txt.
'sort -u inv1.txt > inv2.txt' - to make another copy with the duplicates removed.
'diff inv1.txt inv2.txt | grep name > dupes.txt' - to give you a list of all the duplicated items.
Now you can just open the dupes.txt file in an editor, and use it for reference while you're cleaning out the inventory in world.

/me goes back to being the quiet geek in the corner.