Using the social security number for John A. Comstock from the California site I just mentioned, I went to the site for social security death records -- http://www.ancestry.com/search/rectype/vital/ssdi/main.htmhttp://www.ancestry.com/search/rectype/vital/ssdi/main.htm -- where I found this:
JOHN COMSTOCK SSN 561-50-9438 Residence:92014Del Mar, San Diego, CA Born 30 Jan 1883 Last Benefit: Died Dec 1970 Issued:CA (1954)
One day, I'll find the letter from Dr. Comstock to my stepmother to confirm my recollection that it came from Del Mar in San Diego county. Anyway, I believe this John Comstock from Del Mar is the author of the Comstock book. So, it's too late to thank him personally, but we can help each other out instead.
Good luck in your research, and may you enjoy your new-found relatives as much as I enjoy mine,