David: apart from the fact that I'm sure the Madras Seths were related to the Calcutta Seths, I haven't seen any followup from the Calcutta end of the Seth clan on Genforum.
Anne Basil's book: Armenian Settlements in India from the Earliest Times to the Present Day which was written in Calcutta, records Armenians with regard to their professional or business life. I'm almost sure I saw the reference to a Dr. Seth in it but did not make a copy of that page. I was able to obtain the book by Interlibrary loan through the Toronto Public Library. It is a good followup to M.J. Seth's own history.