Pocket calculator was available in 1972. I remember looking at one in NYC, and wanting it, even though it was only a 4-function calculator. But $200.00 was more than two weeks pay at the time.
Yes. And how many people had them?
The FIRST pocket calculator in San Antonio, Texas was brought in my HS physics class in my junior year (1973).
Now, you're gonna claim that a reserve Lt Col fighter pilot at a reserve air base in Houston was using his slide rule on a hot Texas afternoon to calculate the center points for a proportionally spaced typewriter font to center the heading on three lines of an internal memo that nobody was gonna read?
When that fighter pilot couldn't type?