papers of Dr Gotthelf Bergsträsser

Dr Gotthelf Bergsträsser was an important scholar who disappeared in 1933 while hiking in Bavaria. Does anyone on the list have information about where his papers, his literary Nachlass, are housed (if they are at all preserved)? I am particularly interested in an Arabic alchemical manuscript, K. Inkishaf al-sirr al-maktum, which was in his possession; no other copy seems to be known. J. Ruska saw it and provides information in his Tabula Esmeralda, and this info is repeated by Manfred Ullmann in his handbook n the occult sciences. Many thanks!

Tzvi Langermann