Actually, the patent system is an "honor" system.........
The examiners have no clue what may already be on the market, they research previous claims awarded etc. and it is up to the filer to state the
'unique" aspects of their claims. The PTO then either agrees or dismisses any claims depending on prior art, claims previously awarded and/or things deemed "obvious to those skilled in the art", such as it would be rather hard to claim "a round cylinder as a pressure vessel" being unique to an underwater light design. That is obvious to "those skilled in the art", and virtually anyone else for that matter.
