One of many similar 5-3/4″ x 7-1/4″ presentation cards issued by what is now Macau Post and Telecommunications (Portuguese: Correios e Telecomunicações de Macau; Chinese: 澳門郵電局) to announce new stamp issues.  This one, from September 2023, resembles all the others in style and is fully printed on both sides so technically it is not a postcard.  It could be used that way, though.  Grade: 1