Here is a possible thought:

Maybe the OP's receiver was rejected, for being out of specifications or having a defect, before it received a serial number?

Surplus dealers like, Bannerman's and Stokes Kirk, bought up surplus parts, unfinished parts, and Springfield Armory 'junk', in government auctions.

These two companies built a lot of Krag 'parts guns' in the 1920s and 1930s that often perplex collectors.

There is an area of the OP's receiver that has not looked right to me from the start.

Maybe it is just an optical illusion exaggerated by the removed cut-off and missing wood, or maybe, it is a machining mistake that caused rejection?

I have circled the receiver area that looks odd and kind of gouged to me. I have also included a couple of pictures of that area from a model 1898 and a model 1899 action.

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