How long was the rule of the dynasty that was active when the Rosetta Stone was inscribed?
Ptolemaic dynasty The Ptolemaic dynasty (Ancient Greek: Πτολεμαῖοι , "Ptolemaioi"), sometimes also known as the Lagids or Lagidae (Ancient Greek: Λαγίδαι , "Lagidai", after Lagus, Ptolemy I's father), was a Macedonian Greek royal family, which ruled the Ptolemaic Kingdom in Egypt during the Hellenistic period. Their rule lasted for 275 years, from 305 to 30 BC. They were the last dynasty of ancient Egypt.
Amarna Period The Amarna Period was an era of Egyptian history during the latter half of the Eighteenth Dynasty when the royal residence of the pharaoh and his queen was shifted to Akhetaten ('Horizon of the Aten') in what is now Amarna. It was marked by the reign of Amenhotep IV, who changed his name to Akhenaten (1353–1336 BC) in order to reflect the dramatic change of Egypt's polytheistic religion into one where the sun disc Aten was worshipped over all other gods. Aten was not solely worshipped (the religion was not monotheistic), but the other gods were worshipped to a significantly lesser degree. The Egyptian pantheon of the equality of all gods and goddesses was restored under Akhenaten's successor, Tutankhamun.