What year is your X5? Are you the original owner? As Yii pointed out, that is an OEM battery. If you are not the original owner of your X5 then my guess would be that it is the original battery, unless the prior owner(s) were suckers enough to buy a battery from the dealer.

I think you can get it load tested to see how well it's performing but if it's around 5 years old and/or you live in a hot climate, I would think about just replacing it. Hot weather kills batteries faster. You don't want to wait until it dies and your car won't start. (Ask me how I know.) There are numerous threads on batteries so do a search. There is even information on getting the exact same battery as OEM but without the BMW and BMW part number on it but substantial cheaper. A new battery should not cost you more than about $150. I have a Duralast from Autozone in my X5 and it was about $125.

Car batteries are only manufactured by a handful of companies and rebranded for many others. Johnson Controls is the major one and they manufacture for many, many OEM "brands". Duralast is made by Johnson Controls.

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