Initials/pair of letters on Miller&Val. Greiss 16ga

[steve f]

My Miller&Val.Greiss has 'Nitro' in block letters on the barrels but no date code, so I'm guessing a 1912-1922 proof date? It also has the letters 'HK' on the underside of the barrels, stamped as block letters not script (and the size is pretty small). Would these be a workman's initials?

[mike ford]

steve f,
This is not enough information, to help you. You should post photos of all the markings on the gun, especially of the proofmarks on the underside of the barrels.
Mike