I have to interject........#1 horse shoes were hand forged the majority of the time by the farrier/blacksmith,there is/was no particular style.There are pulling shoes...ones with the "knobs",on the ends,for traction,there were studded,for use on ice,there were corrective shoes for various hoof issues a horse may have,and on and on........not a whole lot has changed from shoes used today vs shoes from 160 years ago,aside from the "blanks",that are purchased now...which are still shaped just like they did way back when.Another thing is that shoes were like tires today,they were in use every where for everything,just because one is found on a battlefield does not prove it was used in any battle action,somebody horseback riding or farmng could have lost that shoe.Also,rust has everything to do with mineral and moisture content of soil,I can show you two metal objects from the exact same period,each buried in different soils have completly different degrees of rust...or no rust at all(matter of fact.....I can show you iron that is dead on 1860,with no rust what so ever)