Which single physical detail, of the man who ruled Egypt for three quarter of a century, remains that is proof that his skin was black and was the first to be a black ruler? What was his name?

I might be wrong here, Mozart, because my source says he ruled for 35 years, but I think the answer is Piye.
Piye was the first of the black pharaohs. The end of his rule was around 715 BC. He was originally from Nubia, which is now largely in the Sudan. Incidentally, Sudan has more pyramids than Egypt:

When Piye died at the end of his 35-year reign in 715 B.C., his subjects honored his wishes by burying him in an Egyptian-style pyramid, with four of his beloved horses nearby. He was the first pharaoh to receive such entombment in more than 500 years.
While hundreds of miles north, at Cairo or Luxor, curiosity seekers arrive by the busload to jostle and crane for views of the Egyptian wonders, Sudan’s seldom-visited pyramids at El Kurru, Nuri, and Meroë stand serenely amid an arid landscape that scarcely hints of the thriving culture of ancient Nubia.
National Geographic

Hi Mozart,
I also found this today:

From Discover Magazine 2005:

But in the eighth century B.C., Nubia turned the tables on its former colonizers. Its armies marched 700 miles north from Jebel Barkal to Thebes, the spiritual capital of Egypt. There the Nubian king Piye became the first of a succession of five "black pharaohs" who ruled Egypt for six decades with the blessing of the Egyptian priesthood.

Yes good answer dance girl. Thank you. For 35 years Piye ruled Egypt -not 75 years. However, The Nubians ruled Egypt for 75 years.

Now, from your first link, on the second page (click continue at the bottom) you will find ----- "On a relief in the temple at the Nubian capital of Napata, only Piye’s legs remain. We are left with a single physical detail of the man—namely, that his skin was dark".

And on page 4, "the ancient world was devoid of racism. At the time of Piye's historic conquest, the fact that the skin was dark was irrelevant. Artwork from ancient Egypt, Greece and Rome shows a clear awareness of racial features and skin tone,but there is little evidence that darker skin was seen as a sign of inferiority". NG

Hi Mozart,
Thank you. Now I see the complete answer you were looking for.

quote:

Originally posted by mozart56:
"the ancient world was devoid of racism. At the time of Piye's historic conquest, the fact that the skin was dark was irrelevant. Artwork from ancient Egypt, Greece and Rome shows a clear awareness of racial features and skin tone,but there is little evidence that darker skin was seen as a sign of inferiority". NG

Really ? But what did their equivalent of pastors proclaim?

I believe that Moses married a Nubian woman.