FWIW - I picked up this relic model 1873 'trapdoor' Springfield at a local gun shop a couple of years ago for $100 (USD). Lots of paint splatter, surface rust, 'black hole' bore, broken firing-pin, no Lock, no butt-plate, no trigger guard assembly, and all the screws were missing.
When the bore cleaned up real good, I decided the rifle was worth salvaging. It took 1 & 1/2 years of careful cleaning and parts shopping, but, it all came together recently.
I had a lot of fun restoring this trapdoor and it is a decent 'shooter'. I probably have a total investment of $385 in the rifle, because, I was quite patient and frugal in procuring parts.
Some before, midway, and after pics:
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