Vanishingly unlikely that a gun that passes proof in 2004 would be so neglected as to justify Teague lining a year or 2 later.
Given that Proof is a potential destructive process of a valuable item, it makes sense to try to avoid a gun making repeat visits.
Proof regulations may take time to catch up with current practice.
It occurs to me that the words LINED might have been inscribed by those (Teague’s ?) who lined the barrels before submitting them to Proof.
They appear to be stamped (presumably with very solid internal support for the liner) but with hindsight it might have been safer to etch them
