First of all, this cup really belongs to the Warring States period, and it is not a crossing at all. What's more, it's not a glass, but a crystal cup. But it is also true. From the appearance, it is indeed similar to the present glass. These two kinds of glasses look equally transparent, and even the production structure is similar to most glasses. But no matter how similar they are, they are just a crystal cup, which was produced during the Warring States period. There are three main reasons for giving this answer.
First, the Warring States had the technology to make crystal cups. In ancient times, crystal was a kind of jade. At least in Shang dynasty, crystals were used to make decorations for utensils. In the tombs discovered in the Spring and Autumn Period, there are many crystal funerary objects. It can be seen that it is very normal to have such crystal cups during the Warring States period.
Second, the design of the Warring States period is the same as that of the present glass. The Warring States preferred to make jade cups. At present, many jade cups unearthed during the Warring States period have been found. Moreover, the design of these jade cups is similar to that of existing cups. It's not surprising that a glass-like design suddenly appeared.
Third, the Warring States has advanced grinding technology and drilling technology. The bottom of this crystal cup in the Warring States period looks like crystal, which shows that ancient craftsmen have learned how to drill and polish. The cups look smoother, indicating that their polishing is also quite strong. In fact, not only this cup, but also a Warring States Cup has been found before, but this one is green, and the design and manufacturing technology of this cup are similar to this crystal cup in all aspects. It can also prove that the craftsmen at that time were very skilled, and it was very simple for them to make such a beautiful cup.
So judging from the above three points, the cup must be from the Warring States period. But we must also admit that this cup is really like a cup now. At first, when experts saw it, they doubted whether a grave robber had been here and put a glass in it, but forgot to take it with them. But it is impossible to think about it. If grave robbers have been to this cemetery, how can the funerary objects in the cemetery be preserved? Sure enough, after careful analysis and study by various experts, they unanimously concluded that this is an antique left over from the Warring States period. After their comparison of history books and exploration in various aspects, it was once again confirmed that this cup could not pass through the past, but it was an exquisite crystal cup made by science and technology at that time.