This is just an unreal specimen to hold in your hands. When Bjorn Borg went to tournaments where Donnay did not want to pay him to use their racquets. Maybe in part due to less or no Television and exposure, Borg's team would have these ones done up and make them all blacked out to prevent any sponsor from being seen. It appears they were painted or sprayed over. It looks to be a Borg Pro or Donnay Allwood all covered up. These are amongst the most rare of Borg racquets due to this fact. As you can notice, this one is just pounded with use which will tells me this one was used over and over again as it looks like a lot of work to make these invisible racquets. You can see the same extra thick base of the racquet as the Allwoods and pros of the era. Just an amazing type find from the Lennart Bergelin collection.
I had seen this in the NHL when the players also wanted to be paid to advertise their brand.