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.