Flag of the President of East Indonesia.
In upload comment for Version 4, I should have said it was a 10:7 aspect ratio, which matches source's image.
However, as User:Mrmw notes, the source states in text 45:30cm, which is a 3:2 aspect ratio.
http://www.hubert-herald.nl/Indonesia%20Timoer.htm
http://www.hubert-herald.nl/Indonesia%20Timoer_bestanden/image016.jpg
State of East Indonesia