After doing my homework, I've now confirmed the full story.
This bass was built by the Brazilian luthier Donda and was originally sold under his own brand, Kempt. At some point, the Sadowsky name was added later.
As I mentioned before, the neck and fingerboard are made of marfim wood, the top is a type of cedar, and the body is mahogany — all of which he personally confirmed.
The pickups and preamp are Bartolini.
Based on this information, it's clear that this is not an original Sadowsky instrument, which is exactly what I stated from the beginning.