Can I tell which copy of a duplicate item was actual used for purchase

[BevS97]

I have searched a little, but am not really sure what to search for so I haven't uncovered anything.

Currently we put all our products in 3 places, by brand, by product type, and by theme. We aren't convined that by theme generates us a lot of sales, but would like some figures to back that up.

Is it possible to tell which copy of a duplicate item has actually been used to make the sale?

[Duncan Rounding]

You're site logs could help, they usually show the referring page. You could look for the add to cart page and then look at the referring page.

[TraceyHand]

not a good option if you already have your duplicates in place but you could add a small reference (a,b,c or 01,02,03) into the product duplicate short descriptions (which are editable) to distinguish one from another?
Not going to help if you're using associated products with associated product names for them either, mind you but could help for a basic product duplication.
If I made any sense?? (not sure I am doing tonight!)