I've taken the driver's side rear door of my 2010 XFR apart to find out why the electrics in it are misbehaving, and to no one's surprise everything in it is wet. I've tracked this down to 3 seals round the fixed glass at the rear of the door, all of which have failed in some way.

1 is around the edge of the fixed glass, this is the one you can see from outside. C2Z10104
1 is a chunky bit of rubber that the fixed glass sits on. C2Z8849

The 3rd one is a mystery. It's a horseshoe shaped piece of black rubber that goes on the outside of the door, around the rear of the fixed glass. It sits between the exterior door moulding and the glass panel. Glass goes in the door first, then this curved seal, then the black gloss trim finisher goes on over the top. Here it is in the workshop manual:

Here is a piece of rear window glass on eBay with the seal piece included, so you know I'm not making it up: https://www.ebay.co.uk/itm/234550681565

However it doesn't show up in the EPC anywhere I can see. It does have a WERS/engineering part number on it, but part of it has rubbed off. It starts 8X23-262A and ends -AB but the bit in the middle is missing. Anyone have a part number for it? I am going to take the other rear door apart tomorrow and see if the engineering part number has rubbed off that one.

It is not C2Z13040 - that is a piece of plastic trim a similar shape that screws on the inside of the door. This seal goes on the outside, but is covered by the finisher.

 

OK, I got the equivalent seal off the LH side (breaking a door finisher piece in the process) and the engineering code on it is 8x23-262a03-ab. I suspect this means that the one on the RH that I need is 8x23-262a02-ab. Is anyone able to translate that into a Jaguar part number?

 

Thank you for posting - Just started my own search on this as my outer seals are sagging and falling out of the finisher track. Thankfully, no water ingress (yet)

 

Here are the rear door quarter window seals from JPART.




#9 - Seal - C2Z2449 Superseded to C2Z10105

#10 - Moulding - C2Z4213 Superseded to C2Z13041

#11 - Screw Cover - C2Z7830 but you should be able to reuse the old one.

#13 - Insulator-Quarter Light Lower - C2Z8850

I think item #10 is what the OP could not find.
All of these look to be good part numbers with some only found on Jaguar Land Rover Classic Parts.
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These guy's ship worldwide and have them in stock for both sides

https://rimmerbros.com/Item--i-C2Z10104

 

Thank you - I just ordered a pair of the outer seals

 

Glad I could help, I've always used them for the genuine Jag spares.
Being in the UK it's a quick turn round for me.