There is no edition by Satavalekar of this Samhita, although his writings indicate that one was planned. So I wonder if there are manuscripts in the Aundh collection of this Veda.
The sole printed edition uses the manuscript at Varanasi (and its derivatives) and covers less than half of the text, as is well know. This edition did not use two manuscripts of the Samhita, probably also fragmentary (but fairly large fragments), contained at the Anand Ashram, Pune. I am not even sure if these two manuscripts have been studied.
Fort Williams College, Calcutta had a large manuscript of the Kapishtthala Katha Samhita, probably complete. The collection of 4000 manuscripts from the institution was transferred to National Library in Kolkata (and partially to RAS Kolkata) more than 150 years ago. I think that this huge manuscript could still be languishing somewhere in the National Library collection, but none of their printed catalogs have any significant information about their manuscript collections (It was with much difficulty that I could even get a scan of the Bharadvajavrittibhashya on Vaisheshika Sutras printed in 1869, with 4 initial pages lost more than a decade ago from there).
Interestingly, the Melukote collection has over a dozen manuscripts of the 'Kathaka Samhita' in Grantha script. Most of them appear to be partial, but at least one was around 300 folios which makes me wonder if these are actually of the Katha Kapishthala Samhita.
In this list around a year ago, I had posted a query regarding details on Swami Maheshananda Giri reporting having studied manuscripts of Kapishthala Brahmana and Aranyaka in early 1970s.
The followers of this Shakha resided in the Tapi River basin from the source Multai down to its estuary in Gujarat, an area that I think not been explored adequately.
Regards,
Vishal Agarwal
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