This is a rare Gimhae Mishima plate made in an official kiln in the early days of the Joseon Dynasty. Calendars and chrysanthemums are inlaid on both sides, with a golden sea on the side and a letter on the back that says Jangkou.
Jangheung is a national warehouse that stores cloth and paper, and was established in Gyeongsang-do, South Korea. In Japan, it is said to have come in handy as a courtesy item for honored guests.
The condition is good, and I think that you can enjoy it with cooking and tea.