Well, buyer beware! Unless it's a reputable rebuilt from Bosch, I've become very leery.
My '82 240D came with a recently-installed, but dead, rebuilt alternator.
Then the replacement Mexican-rebuilt 240D Pep-Boys alternator started working intermittently after six months. Took it back, which of course when they tested it, worked just fine, so no refund or exchange. When I pulled the regulator, I found the armature slip-rings were badly mis-aligned and one of the brushes had worn into the gap between the two rings.
Meanwhile, a friend had given me a couple used Bosch Mercedes alternators. The one I installed on my 240D has been working perfectly for 5 years now.
The other, after a new regulator, has been working fine in my 300TD for 3 years!

Happy Motoring, Mark

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DrDKW