My grandpa had in his attic letters from his great grandpa (great great?? not sure how many generations)'s brother back in Germany, written around 1860. The letters were in the old script not used anymore, and language (Not German, but I'm not sure what it was). Grandpa got them translated and then following the addresses discovered some [great...] granddaughter was living in the house so he sent he a copy of the letters. She then found some cabinet described in the letter and was able to find it in the barn. Until she got the letter that cabinet was meaningless to her, but now that she knows the history it is an important part of her house.

This somehow a point in your question, but I leave it to others to figure out what.

Grandpa donated the letters to the local historical society so they are accessible, though I'm not sure how.