1) The harrows will have been made of wood but they had iron teeth.
1535 It’m vj harrowis tothed with Iron, xxs, Stillingfleet
1578 one oxe harrowe and xxxij iron tethe in it, one horse harrow with xvj iron tethe, Ripley
1606 lez Iron harrowe teeth ... unum Shackle, Thirsk
1639 ‘Arthur Soothill, blacksmith for stealing fowerteene harrow teeth’, Bramhope.