Anyone taken apart rear differential on X5 2003 3.0?

[Bmwe5320023.0]

Counted teeth on my old x5 2002 ring gear, 41 teeth. Counted teeth on the "new" pinion gear, X5 2003, 10 teeth.
So I'm pretty sure the teeth on both differentials are the same, since both differentials are the same as well, 4.10 ratio.
I understand your explanation why the snap rings are different sizes. So basically same differentials can have slight variations.
The only thing I don't understand why now, is why the numbers on the two ring gears are different. Both have 41 teeth looks like.
The differential I purchased from X5 2003 has these letters and numbers on the pinion gear. Not sure what they mean?