With an old Sears catalog?
I’ve often wondered about phone numbers on The Andy Griffith Show like: 371J, or MP-3791 etc. I am in my late fifties but as far as I can remember there was a three digit area code followed by a seven digit number. I must have just barely missed it.
I barely remember telephone exchanges. They were used to represent the first two letters of a 7 digit telephone number. The first two letters of the exchange name are the first two digits of the phone number, when they are spelled out on a telephone dial or keypad. So for example, the exchange name "SYcamore" means that the first two numbers of the telephone number are "79", and SYcamore-4-3317 would be 794-3317. Our old phone number was JUstice-3474.
I went to grade school with a girl, who for years, would vehemently correct anyone who give her phone number as 532-xxxx. "My number is JE2-xxxx," she would insist! (Jefferson was the excchange.)