I have examples stamped on the left and examples stamped on the right side.  My newly minted theory on that is the ones stamped on the left side were the work of old Lewis.  On Friday mornings, after having partaken of Miss Nellie's Thursday night happy hour, would revert to his youth and stamp them on the "trapdoor" side.  I mean, I'm pretty handy with a Dremel but not that handy.

Open your sight and take a photo of the inside of the base.  That will determine the base model.

Level of difficulty?

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That bottom one.  All 1902 ladder and slide bits but 1898c base.  Why?  Why not?  I didn't do it and I strongly doubt somebody had an 1898c base just sitting around waiting for 1902 upper bits.

For what it's worth your sight has the 1898 base.  I'd need to see the inside of the base to confirm.

I'm glad you found the sight page somewhat informative.  It would need a revamp to be accurate but I'm too lazy to bother.  That was the first pass through them.  Subsequent to that I've acquired more examples and started poking at the sub-features.  I guess I can date that page as the Board gun sight isn't there.