This is the national flag of Belgium, according to the Official Guide to Belgian Protocol. It has a 13:15 aspect ratio, though it is rarely seen in this ratio.
Its colours are defined as Pantone black, Pantone yellow 115, and Pantone red 032; also given as CMYK 0,0,0,100; 0,8.5,79,0; and 0,94,87,0.
Date
Source
Van den Bussche, E., Chief of Protocol, Belgian Federal Department of the Interior (2008) Noble Belgique, ô Mère chérie - LE PROTOCOLE EN BELGIQUE (PROTOCOL IN BELGIUM), Heule: Editions UGA ISBN: 9789067689359.
This image of simple geometry is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and contains no original authorship.
Heptagon
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