In US Patent law have provisions for false marketing:-
35 U.S. Code § 292 - False marking
(a) Whoever, without the consent of the patentee, marks upon, or
affixes to, or uses in advertising in connection with anything made,
used, offered for sale, or sold by such person within the United
States, or imported by the person into the United States, the ...
Companies are NOT required to mark their product with patent numbers, but if they do they can demonstrate willful infringement on the patent if you decide to copy the product.
From 35 U.S. Code § 287
In the event of failure so to mark, no damages shall be recovered by the patentee in any action for ...