Your tortoise is a Testudo graeca terrestris, also called the Mesopotamian. They are from desert environments but we don't call them "desert tortoises" because that confuses with the species of Gopherus agassizii and Gopherus morafkai.
The black markings are actually very common in the Mesopotamian. The market for these is what developed the term "Golden Greek" and it stuck, so now almost every breeder and owner uses it. There are specimens that contain much darker coloring, but they are still Mesopotamian. If yours were to breed, not all of their offspring would be purely golden yellow in color. So the nickname "Golden Greek" is actually highly inaccurate. I prefer to call them terrestris or Mesopotamian, as those are true names, but sadly most of the world won't know what I'm talking about.
