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 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.