horse shoes are still being made which makes it hard to date them. Did you find any nails anything else old around them? As far as cleaning them there is a section on the forum Cleaning & Preservation for cleaning objects, everything from electrolysis to chemicals. I am sure someone will come a long and offer better advice soon. Congrats on the horse shoes though. I only seem to find broken ones that are so far rusted they are so brittle if you sneeze you break them.