I have had this porcelain saucers (6) and (7) small plate with a red mark. The mark appears to be a backstamp, which is a common feature on ceramics used to identify the manufacturer, country of origin, or other details.
The red mark is a backstamp, which is often used to identify the maker of a ceramic piece.
The plate is part of a hand-painted porcelain tea set, which may be of Japanese or Chinese origin.
Asking $30. Mint shape.