Frage an die Weltgemeinschaft? Welche Flagge am UN Gebäude ist für Deutschland gültig?

Mr. Johnston Barkat Assistant Secretary-General, United Nations Ombudsman & Mediation Services
Dir Sir,
Having studied flags of all countries in the world I found one gap in the total display of flags. For this reason please have a sight the screenshot attached which shows a flag on the right hand side of the US-American flag which.
Its colour sequence is

BLACK WHITE RED

from top to bottom. I do not know when the video, I took the screenshot from, was taken and because of this I would very much appreciate could you let me know which country the flag attached belongs to.
Please accept my thanks for a soon reply. I remain with kind regards N. Hainzman (Stuttgart-Federal Republik of Germany)