What precautionary measures are to be taken when referring to patent protection?
The marking should be made systematically, without interruption, and not just on certain series of products.

If there is any uncertainty about the scope of protection of a patent or a patent application with respect to a particular product, it is advisable to contact the patent attorney so as to avoid improper or misleading marking.

If the product protected by a patent is distributed by others, it should be ensured that they use the marking properly.