What is Kinfunmei in Japanese Katana terminology?

"Kinfunmei" (金粉銘) refers to an inscription that is written with lacquer mixed with gold powder. This method is used to avoid damaging the tang (Nakago) of the sword.

This type of inscription is often added when a sword that has been greatly polished and has no inscription (Oosuriage Mumei) or a sword that has retained its original state and has no inscription (Ubu Nakago Mumei) is appraised by a sword appraiser, such as the Hon'ami family. The name of the swordsmith or the appraiser, and their signature seal (Kao), are recorded in this inscription."