Terminated: 1983
This calculator (as do many other CASIO scientific calculators) uses one and the same key for both the constant π as well as exponents. This works as follows. When you first enter digits, the "EXP"-key will enable you to enter the numbers exponent, otherwise it will enter the constant π.
One of the disadvantages of this calculator and the CASIO fx-81 is that its power slider wears out rather quickly. Easily fixed by bending the contacts and cleaning them. I was the guy in the classroom that could do that!
Other than that, it is a robust and solid calculator for school usage. The fact that it uses ordinary (AA) batteries that can last for years is also a big advantage.