any use for old pine wood floors?

We currently live in a Victorian that was built in 1889, and I'm not sure how old the floors are, but they seem pretty old.

2 questions...

1) how can you tell how old the floors are? (can you tell?)

2) is there any market for selling the wood? there's not much - maybe 500sqft if it all came up nicely.

the wood itself is in "ok" condition - sanding will make it look much better... the reason we are considering replacing it, is because of the way they did the patch work... they cut straight across the planks and replaced things in chunks.

3) if the floors are original, is it better just to leave it in the house and refinish it, even with the noted patchwork?

thanks in advance for any advice,
Stacy