It seems to be a novelty note issued at a carnival called WIKA (Windhoek Karneval) in Windhoek, Namibia. The carnival was started in 1952 with the goal of honoring German traditions. Here is a link to the one image the official site has of the 1964 prince and princess: https://karneval-in-windhoek.com/ngg_tag/1964/. The people on the note are the prinzenpaar, or royal couple, of the carnival for the year of 1964.