Neither can I.
I have read that it was specific to Winchester.
But the Frank De Hass book / bolt-action bible says it was used by all three manufactures, at various times.
And shows itself when you grind the sight ears off.
What the OP needs to do, is take the scope mount off and see witch manufacture he has.
(Not to mention stripping the white rattle-can paint off and having it professionally re-blued.)
It looks too nice under there for that white paint job!
But at least he didn't paint the bolt & the nice walnut stock too!
rc