At present, most fakes on the market are resin molds. In order to save trouble, merchants often use a real walnut as a mold. Walnuts inverted by mold are not only the same size, but also the same grain. It is out of the question. Pairs of walnuts are hard to find, and you can't pick one.
Extended data:
In order to fake the plastic imitation walnut, dyes have to be added, and the smell of large pieces of plastic is pungent, just like the smell of newly decorated paint. Real walnuts don't smell like paint. If fire is used, it will be accompanied by a pungent smell of plastic.
There are also popular styles of Wan Wen walnuts. Some varieties appeared after 2005, such as Dao and white lion head. If it claims to be a century-old product, it is obviously a lie.