Follow up...
I got a chance to take a better picture of the battery in our 2009 35d. It has what appear to be two different part numbers: S: 61-21-6-946-334 and AW: 61-21-7-586-974. RealOEM.com lists 61-21-6-946-334 as used in a whole slew of BMWs including the E53 X5s but NOT the E70 X5s
FWIW getBMWparts sys that "Part number 61216946334 was superseded by part number 61217586962." 61-21-7-586-974 is not found on either RealOEM of the getBMWparts sites.
Funf Dreisig
Edit: Despite my frequent posts about the unresolved electrical/battery issue(s) in the E70 model X5s, we have not had any electrical problems (yet) on our 2009 35d.
[Knock on head.]