How, by looking at the physical files, to tell the difference between the original photo uploaded to iPhoto, and one of iPhoto's copies of that photo?

(sorry for the poor wording)
Still in the throes of recovering a disk salvage… can’t go by filename or directory… everything is just in one big bucket. Getting pics back online, but now I’ve got dupes, like the original is 90 degrees rotated (b/c camera took the pic sideways)... so that pic is found, plus the rotated upright copy iPhoto made (iPhoto keeps the original around so you can undo anything anytime).

I’ve got 60,000 salvaged files now, would like to get closer to my original 28,000. Because even that is a lot.

And please, no suggestions on backup strategy. It was that that got me in this pickle in the first place.