1 This image shows two right mandible pieces and a full mandible, they were all found within a mile and a half of the same waterway.
2 - They all have one thing in common apart from the fact there all Equus, that is a complete lack of Mandibular Periostitis, damage caused by the use of a bit, on all three examples.
3 - No damage, Work horses race horses etc. were particularly susceptible to bone spurs ( Mandibular Periostitis ) caused by the use of a bit.
4 - The tooth surface on all three examples, show no signs of interference by humans. I have found and excavated many Equus mandible pieces in the becks of south west Cleveland, but am yet to see any signs of Human use.