Sell low. Many manufacturers sell their inventory to other channel dealers instead of specialty stores. In order to clear the inventory, but to prevent the price of the goods from being sold at random and disrupting the normal market price, the manufacturer will wear off the bottom mark. Generally, this will not happen. It is a counterfeit product. After all, ceramic tiles with polished bottom marks generally cannot be sold at a high price, and are even cheaper than ordinary tiles. There is no need for manufacturers to spend more money to polish the bottom marks.