Perhaps the following book(?) by Michael Much will help you:
Visit to Rāhula Sāṅkr̥tyāyana’s collection of negatives at the Bihar Research Society : texts from the Buddhist epistemological school /  Bihar Research Society. Wien : Arbeitskreis für Tibetische und Buddhistische Studien, Universität Wien, 1988. 

a.a.


On May 5, 2017, at 8:39 AM, Péter-Dániel Szántó via INDOLOGY <indology@list.indology.info> wrote:

Rahul Sankrtyayan in his 1935 report wrote that he had seen and photographed a 27-folio ms. of Buddhaśrījñāna's Abhisamayālaṃkāra commentary in Lhasa. 

Does anyone know what became of these photos? They do not seem to be kept in the Göttingen collection (I checked Bandurski's catalogue relatively thoroughly).