Translated from NOS TV in the Netherlands:
While filming for the TV program Tussen Kunst en Kitsch
comparable to the Antiques Roadshow on British TV
According to appraisers the relief is from the period around 1948, when Karel Appel was very poor. He demolished at that time everything in his house to be able to work. In tomorrow’s broadcast it will be announced how much the work of art is worth now.
UPDATE: doubts if it is really by Karel Appel.