There are several ways to label firearms/guns with serials numbers. If the manufacturer applies serial numbers with a laser, there are methods to recover.
How to find serial numbers on a handgun - Quora
How gun dealers are skirting Biden's new ghost gun rule - Marketplace
Do you still remember the serial number of a weapon you were issued in the military? How long ago did you memorize it? - Quora
FNS Service Bulletin
Firearm Serial Numbers - Springfield Armory National Historic Site (U.S. National Park Service)
Wraithworks ARs For The AR-15 Days of Christmas! - Prepper Gun Shop
How to look up the serial number for an Iver Johnson shotgun - Quora
My friend inherited some firearms and noticed the serial number is scratched off. Can he keep it or should he get rid of it? And if the answer is get rid of
Be Mindful of Serial Numbers When Posting Your Gun Photos Online
How to find out my pistol license UIN - Quora