Flag of the Internal Macedonian Revolutionary Organization

The official flag of the Internal Macedonian Revolutionary Organization was adopted in the early 1920s by the Central Committee of IMRO. In 1922, an article was issued by the member of the Macedonian Federative Organization Trifon Grekov entitled "The Flag of Independent Macedonia". It was published in the Bulgarian newspaper "Autonomous Macedonia", and proposed this flag to become the flag of the future Independent Macedonia.

Source: Wikipedia — Flag of the Internal Macedonian Revolutionary Organization (CC BY-SA 4.0)