This is the W-200, a digital wristwatch released by CASIO in 1984.
The diver's watch before the first G-SHOCK introduced previously (CASIO DW-1000) had a diver's icon on the dial, but this model is one of the so-called “marlin models” with a “marlin tuna” icon on the dial.
In Japan, "marlin models” are very popular among CASIO's vintage divers' watches these days, and those in good condition are sold at very high prices in online auctions.
It is called “CASIO vintage Marlin” and seems to be very popular worldwide.

I have several CASIO marlin models that I acquired a long time ago, and this model is one of the rarest.
It is in a slightly scratched condition, probably because it was used hard as a diver's watch.
Other marlin models have the marlin tuna on the dial in “light blue,” but this model is a “white marlin model” with the marlin tuna in white.
The color has not faded with age; the dial frame and the marlin are white from the time of manufacture.
The dial is white with only the words “ALARM CHRONOGRAPH” and “WATER RESIST 100M” painted in emerald green, creating a very well balanced design.

In this model, you can switch between seconds and days of the week by pressing the lower right button when the time is displayed, but as shown in the photo above, the rightmost position only has a larger gap in the lower right segment because of the forced diagonal representation of the “R” in “FR” on Fridays.

The photo above shows the stopwatch mode, but instead of a 1/100 second stopwatch using the lower right two digits, it is a 1/10 stopwatch using the upper right one digit.

The model introduced here has a white dial frame, but there are “orange” and “blue” models with the same model number (W-200) in terms of dial and body color.
The orange and blue models are even rarer and seem to be rarely distributed in Japan. (Models for overseas?)
(Incidentally, the orange and blue models also have white marlin icons.)

As I have written before in the introduction of CASIO F-200, this model also comes up with the current BABY-G (G-MS) and CASIO's electronic keyboard if you simply search for “CASIO W-200”.
I really wish CASIO would stop putting similar model numbers to past models on completely different models.