Terminated: unknown
This calculator has some very peculiar display features, including a slash between digits that can be used to display fractions without loosing a digit (which happens on most CASIO calculators of the same time period).
The overall keyboard layout is quite nice. Also nice is the back-space key.
The OP1 and OP2 keys provide a form of semi-programmability. For instance, when you want to add the number "13/2" to a series of other numbers, simply type + 1 3 ÷ 2 OP1. Now, when you type 5 OP1, the result will be the outcome of "5 + 13/2".
Thanks, Koen van Driessen for this information. Koen discovered more, including a self-test modus of this calculator. Koen’s own website documenting this is no longer active but Mike Sebastian’s website full of "Calculator Technical Information" has kept the information alive: See this page (link validated 2024-10-26).