I never saw a two digit exchange other than the famous one for Samples Sales that Generic mentioned. My phone number as a kid was on the Butler exchange:
BU5-4637 or 285-4637
Odd that things like that stick with you. Sadly I also remember my drivers license number back from when it was a 16 digit number instead of the current SSN format number. It went to the "new" format somewhere between 20 and 30 years ago.
H217-7013-1922-1406
And I remember several long dead application languages (Procomm Plus ASPECT script language - great for calling up your favorite BBS and programming your computer to play a game for you). And how to shift a 20 speed, two stick manual truck transmission...