The key is to look at the application date and ensure that the application date is before the public sale. It may take half a year or more from application to authorization, that is, obtaining rights. This time point does not affect the acquisition of rights.
Therefore, it is enough to submit the patent to the Intellectual Property Office before the public sale.
If the application date after the public sale does not conform to novelty in principle, it cannot be authorized. But in fact, it is much more complicated. Let me talk about the situation of forced patent application after public sale:
Benefits: the examiner may have overlooked that you have sold it, so the patent may also be authorized and the right is valid. You can use this authorization to promote your products or warn your competitors. These are legal rights. That is, if no one pursues it (the lawsuit is invalid), you can get away with it.
Disadvantages: 1, if it is detected, it cannot be authorized. 2. After authorization, the authority is unstable. People who know the details can directly ignore your patent and produce it. If this patent is used for litigation, it is very risky. It is easy to find that your patent is invalid because it does not conform to novelty. Therefore, even if it is authorized, it can only intimidate others and cannot really go to court.