Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
History Stack Exchange is a question and answer site for historians and history buffs. It only takes a minute to sign up.
Was there ever any part of the Netherlands which had this flag?
Guilherme Paula - Public Domain
According to Wikipedia, this is the naval flag of the Netherlands' Secretary of Defense.
This flag would be flown on a ship that the Dutch Secretary of Defense is using as a headquarters (also referred to as a flagship). This type of flag is known as a rank flag.
Required, but never shown