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.
Lakhmids The Lakhmids (Arabic: اللخميون‎ ‎ ) or Banu Lakhm (بنو لخم ) were an Arab kingdom of southern Iraq with al-Hirah as their capital, from about 300 to 602 AD. They were generally but intermittently the allies and clients of the Sassanian Empire, and participant in the Roman–Persian wars.