This is mounted just rear of the side-plate on Model 1899 sn346874 that in all other respects appears to be a legit carbine, has a 1901 Carbine rear sight.

There are 2 threaded bolts into the receiver (does not use side-plate screw). Before I remove it & patch the holes would like to know what it is. I have 20 Krags & and maybe a dozen Lyman/Redfield/Rice/Williams peep sights but have never seen this.

Whatever it is it's probably incomplete, missing something, or is the latch/holder for another piece that is missing. Lever moves back & forth as though it would latch/release something.

Any ideas? Thanks all!

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