This is the "CASIO Janus read sensor" released in 1984.
The model number is AT-552.
At a glance, this model looks like an ordinary ana-digi wristwatch.
Most CASIO ana-digi models have the LCD on the bottom, but this model has the LCD on the top, which is unusual for CASIO.

The reason why the LCD is attached to the upper side is because, in fact, this model is an ana-digi wristwatch with a calculation function, with the entire windshield as a touch sensor (reed sensor) and a handwritten character recognition function!

It is surprising that handwriting recognition was realized almost 40 years ago, although it only recognizes numbers and four arithmetic symbols.
Incidentally, the first generation Apple Watch (smartwatch) was released in 2015, the first generation iPad (tablet) was released in 2010, and the Apple Newton (MessagePad) (PDA) was released in 1993. It shows how CASIO was ahead of its time (too much).
Perverted technology! (a word of praise)

Perhaps because “handwriting recognition” was not yet common, the instruction manual includes a detailed explanation of the handwriting method.
The handwriting recognition accuracy is quite good, but it takes about 0.5 seconds/character from character recognition to display.
Also, the recognition rate for the letter “5” is better if the horizontal bar is written first.

I have introduced various watches with calculation functions on this site, but the ease of use as a calculator is,
CASIO CFX-400
　＞ SANYO_CALCULATOR
　　＞ CASIO AT-552 (this model)
　　　＞ CITIZEN CALCULATOR
　　　　＞ SEIKO DATA-2000
(This is my personal impression.)

Other than the calculator function, there is an alarm function and a stopwatch function (1/10 second), which are operated using the two buttons on the left side.
been interesting to operate the alarm and stopwatch by touching the windshield, or to set the time with handwritten numbers, but unfortunately, this is not a “smart watch” but rather a 1980s ana-digi wristwatch.

Unfortunately, it seems that this model did not sell well at the time, and it is rarely seen at online auctions.
The originator of the current smartwatch is said to be the SEIKO DATA-2000, which was released in 1984, the same year as this model.
If this model had been an explosive hit, the current “smartwatch” may have become mainstream with a completely different concept and design.