LAPL
Years ago--maybe even 15-16, when I had my first computer, I found a site called the Telephone Exchange Name Project; I just went looking for it, and it still exists. But for some reason it seems alot less accessible in terms of searching than it did back when I was a computer novice. Anyway, it seems that the GLadstone-4 exchange was more or less specific to Pacific Palisades. Apparently Malibu had a GLobe exchange--seems it was typical for extensions of an existing exchange to use the same first two letters but a different name. Gladstone's--the seafood restaurant--is actually in Pacific Palisades, and its phone number was an early example of the common use now of marketing via the telephone dial. (The number is still GLadstone-4-3474.) I do know that telephoning in Los Angeles evolved from the early days of using colors:
http://freepages.genealogy.rootsweb....on/s99_209.htm
to a single letter to exchange names, and from exchange-name-plus-4-numbers to exchange-plus-5-numbers, etc. Here's a fairly simple list of L.A. exchanges:
http://www.laalmanac.com/communications/cm01e.htm
And here is an interesting set of pictures of all the various exchange buildings around L.A., including the GLadstone in PP. Unfortunately, the creators haven't included the specific addresses of the buildings:
http://www.thecentraloffice.com/calif/LA/LAindex.htm
Gary's Antique Telephone Collection