There is nothing written in stone as far as pronunciation, as long as you’re not the only one in a particular area of the country who pronounces words differently from the rest. I’m from California, so to me the pronunciation of “interesting” and “diamond” as pronounced above sound like they are from somewhere else. I thought someone might recognize where in the country they are pronounced like that. Now I’m starting to think that it is somewhere on the East Coast.
The name of the narrator is still a mystery. As a matter of fact, I am trying to isolate a specific area of the country in relationship to this question: http://boards.straightdope.com/sdmb/showthread.php?t=651147
Maybe this time, somebody will know who the man is/was. It is not somebody whose name we might recognize today. If you can find his name on the Internet, who have the wrong person, unless you have another source of information.