I'm going to descent from the rest of the pack
....and call it dark (dunkel) poplar.
Since there's no model/model year/build date info...I can't specifically identify where in the production run this X5 falls...but there were multiple "poplar" woods used:
- natur (natural) poplar
- raunchgrau (smoke gray) poplar
- dunkel (dark) poplar
- hell (light) poplar
And I'd assume that the sticker on the back (BMW E53 DP F LH) is probably interpreted as
BMW E53 Dunkel Poplar Finish Left Hand. Granted, it can be difficult with wood coloring sometimes since the finish can naturally be slightly different (since the wood veneer is real)...then there is sun/ultra-violet fade as well.
Below is a pic of hell (light) poplar wood...compare the finish to z168...and there is a noticeable difference:
(hell {light} poplar wood trim)
I could be wrong, but that's my reason for the descenting argument.