I had previously noticed news articles about buttons made from potato, but was a bit sceptical. However, information about these buttons appears in the”German Button Industry” BIOS report.
” A considerable stock of Anras Sheet material was found which was a Casein substitute material made from potato starch by Messrs. Anras Combine at Veendam. Production of Anras buttons was similar to normal Casein production but the material was very hard and could not be polished with a chemical polish.” The report then details how both Casein and Andras buttons were polished in five stages that took 4-6 days!
Here is the earliest article I found in Trove:
and the latest: