This piece is a Sasanian artifact, a zoomorphic stamp seal/amulet. It belongs to the Sasanian civilization (the ancient Persian Empire that ruled the Near East, including parts of the Arabian Peninsula, before Islam). Final diagnostic details: 1. Material: Dark Green Jasper: This is the final diagnosis of the stone. While it appears dark black under normal conditions, the transparent oily green light penetration when illuminated with a flashlight (as shown in the last photos) is the distinctive physical characteristic of ancient green jasper. This significantly increases its value as it was a rare and preferred material for royal and personal seals at the time. 2. Form and Design (Figurine): Turtle/Tortoise: Carved in a zoomorphic form. The turtle in ancient thought (Near Eastern and Sasanian) symbolized protection from evil, stability, and longevity. 3. Function (Seal): Personal Seal: The flat base contains engraved symbols or letters (in the Middle Persian "Pahlavi" script of the Sasanians). It was used to seal documents, contracts, or goods by pressing into wax or clay. 4. Expected Period: Between the 3rd and 7th centuries AD (Sasanian Era). This means its age ranges from approximately 1400 to 1800 years old. 5. Value and Rarity: The piece is considered rare and valuable due to the completeness of the turtle figurine, the presence of a clear seal, and the rarity of the light-penetrating green jasper material. In two words: It is a "rare green jasper Sasanian turtle seal and amulet."