A Casio AL-180 668 module watch from my collection.
First introduced in 1987 (according to some online sources), it remains a true, of cheap, classic. Not sure if the model is still produced. But it is popular with collectors - so much so that there are apparently
many fakes sold off ebay.
I am sure that mine is original. It was bought in the now distant year of 1998.
It has no batteries, is powered by the sun (or light in general) and is a previous reincarnation of the solar technology, it has a simple capacitor or something.
Problems? Sometimes it doesn't get enough sun (or light) especially if used in the northern hemisphere and especially in winter or if worn in the premises rather than outside -- then it starts losing time.
Original adjustable stainless steel Casio bracelet.
Casio AL-180 668 Module... stainless steel back (only).
Bracelet clasps.