Casio MQ-2 (Micro Quartz)
Distinctive features: Tiny calculator with clock, stop-watch, and alarm. Can perform time and date calculations.
Technical details:
Display is 8 digits, LCD (yellow-filtered to cut out wavelengths of light harmful to the LCD).
4-function, time and date calculations, clock, stop-watch.
Input for date calculation is limited to January 1, 1901 to December 31, 2099 (so is Y2K compliant), taking leap years into account. It can calculate the number of days between two dates.
Battery: Two G-13 button cells (1.55v silver oxide).
Size: 121 x 36 x 11mm (4.75" x 1.4" x 0.4").
Made in Japan.
Note that since it is a clock, there is no on/off switch.
The MQ-2 is slightly larger than the MQ-1 and has an 8-digit display, instead of 6-digits, and an alarm.
Significance:
With advances in electronics and by using a liquid crystal display (LCD) it became possible to include a clock with the calculator where the display was continuously on. This was a great advantage over the previous Casio CQ-1 model with its power-hungry VFD display.