1921 AD., Germany, Weimar Republic, Free State of Brunswick, Kraftverkehrsgesellschaft m.b.H., Notgeld, collector series issue, 50 Pfennig, Grabowski/Mehl 156.4a. Reverse

State: Germany, Weimar Republic
Issuer: Kraftverkehrsgesellschaft m.b.H. Braunschweig
Location of issue: Brunswick, Braunschweig,
Date of issue: 1.7.1921 AD.,
Value: 50 Pfennig, red overprint on 1,60 Mark
Size: 96 x 64 mm
Material: paper
Watermark: -
Serial : -
Serial no. : -
Signature: - (0)
Printer: Druckerei Appelhans, Braunschweig, designer: Franz Albert Jüttner
Obv.: Mark/0,50 - Mark/0,50 / Kraftverkehrsgesellschaft / m.b.H Braunschweig / (Staatlich kommunaler Betrieb) / Dieser Gutschein …. , Brocken spectre leaning on Brocken mountain.
Rev.: Mark/0,50 / F. Jüttner 21. / Kraftverkehrsgesellschaft m.b.H Braunschweig , bus driving left, scared passengers on top, above, witches riding on animals and brooms.
References: Grabowski/Mehl 156.4a .

Franz Albert Jüttner (häufig auch nur Franz Jüttner, * 23. April 1865 in Lindenstadt (poln. Lipowiec) bei Birnbaum, Posen; † 1. Mai 1926 in Wolfenbüttel) war ein deutscher Illustrator, Zeichner und Karikaturist. Er war Mitarbeiter des Kladderadatsch und nach Gründung der Lustigen Blätter 1896 deren meistgedruckter Zeichner. Ein weiteres Tätigkeitsfeld eröffnete sich mit der Gestaltung von Notgeldscheinen, bei denen er historische Motive grafisch umsetzte.
More on https://de.wikipedia.org/wiki/Franz_Albert_Jüttner

A Brocken spectre (German: Brockengespenst), also called Brocken bow or mountain spectre, is the magnified (and apparently enormous) shadow of an observer cast upon clouds opposite the Sun's direction. The figure's head is often surrounded by the halo-like rings of coloured light forming a glory, which appears opposite the Sun's direction when uniformly-sized water droplets in clouds refract and backscatter sunlight.
The phenomenon can appear on any misty mountainside or cloud bank, even when seen from an aeroplane, but the frequent fogs and low-altitude accessibility of the Brocken, a peak in the Harz Mountains in Germany, have created a local legend from which the phenomenon draws its name. The Brocken spectre was observed and described by Johann Silberschlag in 1780, and has since been recorded often in literature about the region.

Goethe described the Brocken in his Faust, first published in 1808, as the center of revelry for witches on Walpurgisnacht (30 April; the eve of St Walpurga's Day).

Now, to the Brocken, the witches ride;
The stubble is gold and the corn is green;
There is the carnival crew to be seen,
And Squire Urianus will come to preside.
So over the valleys, our company floats,
With witches a-farting on stinking old goats.

Goethe may have gained inspiration from two rock formations on the mountain's summit, the Teufelskanzel (Devil's Pulpit) and the Hexenaltar (Witches' Altar).

More on https://en.wikipedia.org/wiki/Brocken_spectre ; https://en.wikipedia.org/wiki/Brocken