Post #608808 by Otto on Sun, Oct 2, 2011 8:41 PM

Vampiress RN was nice enough to PM me directly (and not publicly here, thereby letting everyone know I can't search Wikipedia myself) and let me know that this info is readily available on Wikipedia although its frustratingly vague.

Here is what Wiki says:
the two digit letters referring to an area, followed by the third number "generally happened after World War II, although New York City did this in 1930. Thus, the famous Glenn Miller tune "PEnnsylvania 6-5000" refers to a telephone number 736-5000, the number of the Hotel Pennsylvania, which still bears the same number today. Similarly, the classic film "BUtterfield 8" is set in the East Side of Manhattan between roughly 64th and 86th Streets, where the telephone prefixes include 288. This is why, in some works of fiction, phone numbers will begin with "KLondike 5" or "KLamath 5", which translates to 555, an exchange that is unused in most areas.

The letter system was phased out, beginning before 1965 (though it persisted ten years later in some places, and was included in Bell of Pennsylvania directories until 1983)"

So the addition of the numbers could be anywhere from 1930 - 1951, maybe?
and the disappearance or transition away from letters is somewhere between 1965 and 1975, or 1983 if you are in Pennsylvania!?!

I was specifically wondering in regards to this post
http://www.tikicentral.com/viewtopic.php?topic=40053&forum=2&vpost=608802
So specifically my question would be, when did the letters stop being used in the Oakland area (Northern California) on business postings such as ads and match covers