Like yourself we live in an old farm house (1870's). I may have missed some of your postings but what kind of metal detector are you using as to brand, discriminator?,
batteries type.? etc.? Not long ago I got a faint reading at one end of the front porch
and it proved to be at about three inches an Indian head penny, that someone had drilled a tiny (1/16")hole in (watch fob maybe?), The fool who drilled it had drilled out the third digit of the year date so it could be 1860, 1870 etc . My other coin finds was a silver dime at the old (1850's) site of a Missouri Jayhawker in the Kansas Border Wars named George W. Clarke. It also had a hole drilled but the date was 1835. I bought a silver pendant frame put the dime in and gave it to our daughter for a birthday present.
Keep at it, there are many wonderful things waiting for you to dig them up.