During World War Two, the Allied powers along with the Germans and their allies (excluding Japan) communicated specifics required by the Third Geneva Convention to each other through the International Red Cross. The most important information communicated was the name and rank and identification number of each newly captured prisoner of war. Mail between POWs and their families went through the International Red Cross. POWs were not allowed to write to one another.
German POWs in the United States (there were eventually almost 400,000) organized classes in every subject conceivable in their various camps. In May 1944, the Reich Ministry of Education issued detailed instructions through the International Red Cross to these men, specifying which German universities would accept their educational credits and how these were to be documented.
At the same time, also through the offices of the International Red Cross, German Armed Forces High Command issued to each German POW held by the United States, a 40 page booklet, Studiennachweis fur Kriegsfangene, or Evidence of Study for War Prisoners. These booklets were printed in Germany, sent to the International Red Cross in Switzerland, which shipped them to the United States whence they were distributed to German POWs by the American Red Cross. (Similar action being taken in other countries holding German POWs.)
These booklets served as certified transcripts and each student who passed a course had this book or another form signed by the class instructor then counter-signed by the American camp commandant. (All German POWs in the US were in the official custody of the US Army Provost Marshal and all POW camps were administered by the US Army.) German POWs were also allowed to take correspondence courses from various American universities.
[Images courtesy of Alabama Heritage, published by the University of Alabama.]