Terminated: 1980
No screwing is required when replacing the batteries. A small slider at the back provides access. This slider however does open a bit too easily. The sleeve however is made such that accidentally opening of the slider can not occur.
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.