Unlike modern firearms, which almost universally stamp serial numbers on the receiver, vintage Belgian shotguns followed a different set of rules. If you are currently inspecting a Neumann Bros shotgun and cannot locate the serial number, do not panic. It is likely there, hidden in plain sight or obscured by a century of use.
: The classic Belgian proof mark from Liege, indicating acceptance by the Belgian proof house. Neumann Bros Shotgun Serial Number Location