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>> 141, obviously a rear rifle sight, perhaps a Mauser version or Krag. >
> It is a gun sight, but I don't know what type.
It looks very like Mauser, rather than Krag. I've also never seen one bent like that so I'd guess it has been bent after leaving the factory. Front-hinged, so it has the "roller coaster" type assembly on the top of the barrel that the elevation slider adjusts on. Initial guess is 1893 or newer; the 1891 had the hinge pin at the other end. I can take a look tonight to see which of my Mausers' sights this matches, but it's 1893 or later.
Dave Hinz