This is called the "waakvlam", the "pilot-flame" of the Police.
Stefan Lambregts, 12 Sep 2003
New Dutch policeflag (variants)
by Jarig Bakker, 25 Sep 2003
I've passed several times the police-office on the Raampoort in Amsterdam,
which has an impressive flagpole, wound in some blue cloth, which seems
to be disentangled every 10 years, preventing our citizens to admire it
(the blue cloth and what's on it); however on the main office at the Elandsgracht
the flag is on top: blue with white letters POLITIE, and some brown emblem
(the same as Shipmate has).
Jarig Bakker, 25 Sep 2003
Two pictures of the flag of the Netherlands National Police (Nationale
Politie) that I took in Amsterdam. The flag is different from the
two pictured in FOTW. Motto on flag is: «waakzaam en dienstbaar»
appears to be what I saw.
Images of previously used variants:
I also ran across an image of the Netherlands Ministerie van Justitie flag.
Dave Fowler, 9 July 2016