I think your seats might be replicas, I have a couple of sets of factory ones and the differences I can remember are:
- Porsche logo should be embossed top center in the leather
- Stitching is different on the back cushion
- Stickers with 996. part numbers, I've never seen a badge like yours before
I would guess they're worth $500ish, you can do a search for replice gt3 seats.
This is a picture I found in which you can see some of the differences:
