I became interested in airlines in the early 70's. We lived just east of Lambert - St. Louis International Airport, which meant that several hundred landings or departures were readily visible each day. I would "borrow" my father's bonoculars to "watch the airplanes" for hours on end.
In late 1972, I decided to call each airline to see what they would be willing to send me (preferably pictures of their aircraft). The first call went to Allegheny, and they sent me a timetable. I had never seen a timetable before and dug into the 80 pages with gusto! Since it was winter (too cold for plane-watching), I had plenty of time to spend with my new treasure, and practically wore the cover off. It's pretty beat up, and even though I have a better copy of this issue in my collection, I keep it as a reminder of how it all began.
After receiving this first timetable, I was on a mission to get timetables from all of the other airlines. Only afterwards, did I realize that the Allegheny timetable was somewhat of an oddity.
Back in the days of columnar timetables, airlines often used symbols at the top of each column to represent different aircraft types. (In fact those symbols were fairly standardized, so each symbol usually had the same meaning from one carrier to the next.) When airlines switched to the quick reference format, they normally designated different equipment types either by listing the aircraft type as part of the flight info, assigning certain types to ranges of flight numbers, or color-coding the schedules to indicate a certain type. The Allegheny timetables of the early 70's retained the use of symbols to indicate the aircraft type; i.e., the circled triangles indicated DC-9's, circled diamonds were BAC 1-11's, and the circled club symbols were Convair 580's. (Those club symbols had been associated with the Convairs since the 1950's.)
In 1974 Allegheny discontinued the use of symbols, replacing them with a listing of equipment based on ranges of flight numbers.