Since you’re going to remove the oxide layer from the flashlight, you should take the opportunity to clear coat them to prevent future oxidation. If you dont, they will quickly oxidize again once your customers removes them from the packaging.
Astrolux clear coated their copper FT03 SBT90.2 lights, and mine still looks brand new after 4 years.
thanks your suggestion, as such flashligt so big and didnt quantity produced, and it will become patina at last after years. so we didnt coat it. other small ones will do it like that with coat in the future.