The earliest reign-date chops yet discovered are two chops carved with the characters for the Chen-kuan and K'ai-yuan periods in the calligraphy of the T'ang emperors T'ai-tsung and Hsuan-tsung.
唐太宗、玄宗親書，由工匠刻成的「貞觀」、「開元」二印，是目前發現最早的紀年印；而齋館軒堂印之始，則相傳起於李泌的「端居室」一印。