Thank you, Matthew, Peter and Ryan, for your suggestions. The geographic web site is quite addictive and a useful resource! Thanks for that.
Ryan, your pointers are also helpful. Do you have any indications that others in that region also identified as Sāṃmitīyas? In addition to saying his parents were brahmins (suggesting a brahmanic upbringing which might be why his Sanskrit was so impressive), he also says of himself:
[As for my] knowledge (yon tan), [I] am practiced in Madhyamaka and Pramāṇa. I know by heart the commentaries [made] by Devendrabuddhi and Śākyabuddhi on Dharmakīırti's Pramāṇavārttika. In addition, I am well versed in the commentaries on Prajñākaragupta, Dharmottara, and Yamāri…
[My translation from Caumanns’s German translation]
[Was meine] Kenntnisse (yon tan) [angeht, so] bin [ich] im Madhyamaka und im Pramāṇa geübt. Die Kommentare, [die] Devendrabuddhi und Śākyabuddhi zu Dharmakīırtis Pramāṇavārttika [verfassten], kenne ich auswendig. Darüber hinaus bin ich auch bewandert in den Kommentaren des Prajñākaragupta, des Dharmottara und des Yamāri.
It’s as if, while being a Sāṃmitīya, he is offering a cv touting his expertise in the doctrinal qualities (yon tan = guṇas) desired and in demand at that time from possible Tibetan patrons.
thanks,
Dan