It looks like a box that a 35mm Kodachrome film would be sold in

The "calculate before" date gives some indication of when this calculator was made

There is a "window" in the canister that the LCD appears in when the "film" is pulled out.
The "film" is the keypad.

I don't know if the keypad or the LCD work as the battery has expired and, as yet,
I don't know how to get inside without damaging the calculator.
I just hope the battery hasn't leaked and done too much damage...

Well, I decided to have a go at getting into the calculator...
I soon realised that the end caps are glued on.

Eventually I managed to remove one end cap and slide out the "innards".
While trying to dismantle further in order to replace the battery,
I managed to crack the very delicate LCD.

The "underside" of the board. On the right is the battery location.
The 392 / AG3 battery was held in place by a metal clip, soldered on 3 sides.
Fitting a new battery showed that the keypad still worked, but with the cracked
glass the display shows incomplete digits.

This set of images © Barry Smith, 2008