Metric to imperial conversion was not as easy in the 1980s as it is today.
Today you can just open a web browser and enter a plain english statement like “convert 37.4 celsius to fahrenheit” and Google will helpfully give you the answer in a fraction of a second. It also tells you the formula is (celsius x9/5) + 32. In the 80s you’d have to remember that formula, or look it up. And if you wanted to convert it the other way, you’d have to remember the formula is (Fahrenheit − 32) × 5/9.
Enter Casio’s Metcon calculator in 1985 — the CM-32 (and CM-321 in a metal case).
A couple of years before this, you could buy a desktop calculator that would do conversions for you, but this was the first that did so in a wristwatch.
To use it, you’d enter calculator mode and enter your number to be converted. Then press the recessed side button once or twice (depending which way you wanted to do the conversion) and select the key with the conversion you want.
Feet to metres, miles to kilometres, temperature and more; this calculator watch did it quickly and easily.
While it didn’t come with a game, this calculator watch was probably more useful to the 1980s student than the similar-looking CA-51.
I don’t know how many of these Casio produced, but they are rare these days and have never been seen in great numbers.
The QW458 module can only be found in the two CM-xx watches although Casio have produced several metric converter calculators over the years, one of the earliest being the MC-800 which would have pre-dated the CM-32.
While it’s a bit of a one-trick pony, it’s a great trick the CM-32 offers and is one of the best of Casio’s mid-late 80s calculator watches. Prices can vary – you can get one for a bargain if you keep a close eye on eBay, but can also sell for several hundred dollars in excellent condition.
I got this one in nice condition, but missing the strap. A generic strap just won’t cut it on a Casio of this era (or any Casio, really) and I was lucky to find an original replacement. Original straps are often harder to find than the watches themselves, and are expensive for what they are, but are worth every penny in my opinion.