Hello Vera,
I think that this seed is a species of Guizotia, but not the cultivated G. abyssinica (oil, food and birdseed). There are species in Eastern Africa that appear similar to the imaged seeds such as G. scabra and G. villosa.
I found one paper online that has images of these wild Guizotia seeds (on page 15): Geleta, M. 2007. Genetic Diversity, Phylogenetics and Molecular Systematics of Guizotia Cass. (Asteraceae). Doctoral Dissertation.
There is a drawing of G. villosa seed on the United States National Germplasm System (GRIN) website: https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomydetail?id=450166
Please let me know what you find out!
Thank you, Jennifer