Mystery Marking (WLH/10/56)

[Beerhunter]

How did potentially lethal (to the shooter) rifles get surplussed by the army without being disabled?

Simples! The British Government is exempt from the Gun Barrel Proof Act and therefore relies on the private sector (which is NOT exempt) to have military surplus firearms Proofed before onward sale. This has happened in the case of your rifle as is evidenced by the London Proof marks on it. And, so in this case the system has worked and the ZF mark is trumped by the civilian GP (Gunmakers Proof).