Some of these Casio watches on the Internet are completely inferior imitations, and some are actually the same movements as genuine Casio, but the production and assembly of parts such as casings are all completed by small workshops. Casio's big three-needle style movement and chronograph style movement basically adopt the Meidaita movement owned by Japanese citizens. The cost of this movement is relatively low, and it can be bought. Many imitation watches JS are faked by this. Although the movement is the same, the shell is rough and the key is that the waterproof performance cannot be guaranteed. But then again, the Casio market is hot and the knockoffs are widely sold. Casio imitations in China are very mature, and the quality of imitations is also divided into 369 and so on. Therefore, although the quality of Casio imitation goods is far from being compared with the genuine goods, the imitation goods with relatively good quality are not bad enough to be unusable. After all, the price is there, so it's ok to buy one and play with it.
If you want to buy genuine Casio watches online, you can actually choose those G-SHOCK products with solar energy and radio wave functions, because it is impossible to make fakes in China-there is no technology and the cost is high. However, the corresponding Casio watches are not cheap online, not so much lower than the counters.
I hope it will help you and be adopted as a satisfactory answer.