Pre-1893 and likely pre-1891. Note forward of the "Laminated Steel" (the barrels are Twist) is the place where "Belgium" was usually marked.
It was not until 1891 that the U.S. required the country of origin to be clearly marked on an imported gun.
It does not carry Smokeless powder proof, which at that point was voluntary and would have been with "E.C." or "Schultze"