Yours looks to be for a M1917 or a P14 as mentioned - will be different markings / different lengths to confirm which it was. The clip, the main slide body and the base ladder part might all have maker marks - "E", "R" or "W". It appears to have had its long range aperture cut off and removed from the slide, which makes that part of it useless. The P14 sight ladder is longer - 2.43"; for the M1917 it is 2.16" long. They will interchange, but sighting ranges will not be correct. The longer P14 one, on an M1917, will interfere with using a charger. Information is from Charles Stratton book, "Pattern 1914 and U.S. Model of 1917".
Another way to differentiate - for a P14, on the top cross bar of the rear sight ladder - on the face that is against the paper as in your picture, there will be the serial number for the rifle that it was installed on. If no serial number, it is likely for an M1917. Numrich (gunpartscorp) in USA showing that P14 rear sight assembly (with complete slide) for $US 30.75 - the small bits are also available separately. They show Out Of Stock for the equivalent complete assembly for a M1917, but do show some parts that go with it - main leaf spring, axle pin, etc. for it, in stock.