Brand: CASIO
Model: fx-82ES PLUS
Type: Scientific calculator
Picture: CASIO fx-82ES PLUS
Batteries: AAA x 1
Lifetime: Introduced: 2013
Terminated: unknown
Notes: The CASIO fx-82 series started with the CASIO fx-82, an ordinary scientific calculator. But But CASIO kept extending this line, turning it not into just a model number but a whole calculator series. Trying to make it the non-programmable scientific calculator for school use.

So far I've found mention of the following types:

This calculator has NATURAL-V.P.A.M. that supposedly stands for "Natural Visually Perfect Algebraic Method". This calculator tries to be accurate when it can. For instance, when dividing 1 by three the answer displayed is "1/3". To switch between mathematical and decimal results the "S◄►D"-key can be used. To see it as a decimal result one can also press "SHIFT" "=". This is not indicated on the keypad.

The "MODE"-key can be used to specify this behaviour. It can be used to switch between normal mode, statistics, and table calculations. To do more settings one has to press "SHIFT" "MODE". There it is possible to switch between "MthIO" (mathematical results) and "LineIO" (decimal results).

This NATURAL-V.P.A.M. is actually quite good. For instance, when the calculator is set to RADians, calculating "SIN(π/4" will produce the answer "√2/2".

It can also be used to convert decimals into fractions. For instance, typing "1.234" and then the "="-key will display "617/500".

The way this calculator works is very natural (hence NATURAL?). For instance, when entering a number, and the pressing "SIN" will show "SIN(". When pressing the "="-key this is automatically interpreted as "SIN(ANS)". "ANS", the previous result, is automatically entered when ever that is logical.

It has a REPLAY function to edit previously entered calculations.

For a scientific calculator it has quite a lot of functions. Many statistical functions, a special mode to calculate tables of a formula with a specified step size.

This calculator runs, despite its thinness, on a single AAA battery. The battery is actually used, the top part of the backside has an AAA battery shaped part that is used to slightly tilt up the calculator. Its battery life must have been phenomenal.

This specific specimen I found at a flea market has had its necessary amount of wear and tear. Many of its keys lost their markings. It still works beautifully. I could only try it out after finding its manual on-line.