Harrington & Richardson generally etches serial numbers on the butt of a gun's grip and the bottom of the top strap. H&R gun owners' manuals provide detailed information about the location of serial numbers on individual guns.
Some H&R gun designs require removing the grip cover or the top strap to see the serial number. H&R may etch the last three digits of a gun's serial number on custom or accessory gun parts. Before the Gun Control Act of 1968, manufacturers did not have to etch serial numbers onto guns, so some older H&R guns may not have serial numbers.