signet ring; seal ring
A ring with an engraved seal used for stamping documents. The term is specific and not an everyday word; it may be encountered in historical or formal contexts.
He stamped the document with his signet ring.
Compound of 認印 (みとめいん, 'personal seal') + 付き (つき, 'attached') + 指輪 (ゆびわ, 'ring'). The exact historical derivation is uncertain; the term describes a ring that functions as a personal seal.