I am trying to identify this man:

This is from an English course called "Modern American English," marketed by
Grolier around 1970. It had a number of narrated articles and stories
narrated by him. He was also a narrator on "Grolier Programmed English,"
copyrighted by Grolier in 1978.

The man was a superb narrator, but apparently he never became well known, so
I do not think he is a name we might recognize today. He does sound a bit
like John Forsythe or a young Lee Bowman, but he is neither. There is
already a Wikipedia article saying he is Leslie Daniel, but that is also wrong.

At this point, I seriously think that to know who he is, you have to know
something about the history of narrators from back then, narrators who
worked for Grolier, or something of the sort. Others and I have been trying
for awhile to match the voice to that of people one might hear on TV, for
example, with no success.  I've asked in some specialized forums, but not
luck either. Grolier was taken over by Scholastic some years ago, but they
are not too interested in the past and have been uncooperative.

Thank you.