For historical authencity, the exchange would be of the name that
> once served where the phone will be used. However, it's very
> possible no such name was assigned there; in the past it may have
> been a five digit exchange or newly created.
By the time all-number calling was in use, the 302 phone was generally on the way out.
Around 1950 I lived in a city (Konawa, Okla.) where telephone had either three or four digits. Area codes were just being introduced and mostly for operators. Most of the public had never heard of "area code" nor knew what the term meant.
That was near the twilight days of 302 telephones.
As the 500 set was only introduced in 1950, it took quite a bit of time for it to replace existing 302 sets in service. (A family member had one until they rennovated their house). I suspect the Bell System continued installing 302 sets well into the 1950s. Some were placed in a pseudo-500 body and called a 5302.
In 1970 it was not unusual to find a 302 or 354 (wall) set in a home.
In the 1950s, even into the 1960s, many smaller towns had five digit numbers. They got a seven digit ANC number to be addressable by DDD, but for local use continued with five digits (into the 1980s until ESS came along). Those places obviously never had a named exchange.
But larger towns and cities did have named exchanges, some seven digits, a few six digits. Those names appeared on the number card. In the older days the full name appeared, with the dialable letters in capitals, often several points bigger than the rest of the name. In later days for places that didn't go ANC, often only the two letters appeared with the area code.
When area codes came out a sticker was mailed to homes to be placed over the "WAIT FOR" portion of the number card. It obviously took a long time between actual area code assignment and wide use of it.
Before that, many people placed calls by only name and town, not even the number. As part of placing the car the operator got the distant Information to get the number. The Bell System ran a campaign to discourage that "Call by Number and save time!" years ago. You can see people do it in old movies.
I remember being in or seeing pictures of school buildings built new in the mid-1950s and the school office was equipped with 302 sets. So, they were still installing them in new installations even after the 500 set came out. Perhaps a more prestigious new office or residence got newer sets.
In the early 1950s some areas with rapid development had shortages and had to wait for telephone service. I suspect those people were happy to get any set at all just to have service. I don't think the Bell System had the luxury of throwing out a massive inventory of 302 sets in those days, but rather reconditioned them back to service.
Heck, I'm told that in the early 1950s plenty of people still had candle stick phones. At one time they were cheaper than handset phones. Certainly plenty had 202 set (the "French" handset phone). Many payphones of the 1950s had two piece transmitter/receiver.
One upgrade the Bell System did make was to put on "F" units (the 302 transmitter and receiver) on candle stick and 202 sets since the quality was far superior. Many 202 sets had an E base but an F handset.
Privately owned/operated internal telephone networks seemed to stick with AE 40 gear for many years, never getting upgraded to say an AE
Thompson, Manitoba had a 677 exchange when the town was first built in the very early 1960's but the locals only dialed a four digit number. Some time in the mid to late 60s a 778 prefix was added. You only needed to dial the 8 for the 778 phone numbers and continued to dial four digits for the 677 numbers. The government owned Manitoba Telephone Systems (MTS) is the telco.